Quick connect parameter exchange

ABSTRACT

The startup, retrain, renegotiation quick connect or other processes of handshaking between communication systems involve the exchange of certain modulation, constellation, precoder, prefilter and other communication related information. The communication systems exchange one long information sequence including all the necessary communication information. Subsequently, the communication systems start transmitting short sequences, including an acknowledgement information portion. If one of the communication systems does not receive an acknowledgement within a predetermined time or event, that communication system may retransmit another long information sequence. After such retransmission, the retransmitting communication system may continue transmitting the long information sequences or may start transmitting the short sequences once again. Eventually, each of the communication systems should receive a long information sequence and acknowledge their receipt of such sequence.

RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.09/557,233, filed Apr. 24, 2000, now U.S. Pat. No. 6,704,399, which is aContinuation-In-Part of U.S. application Ser. Nos. 09/416,482 and09/393,616, filed Oct. 12, 1999, now U.S. Pat. No. 6,785,371, and Sep.10, 1999, respectively, which are both Continuation-In-Part applicationsof U.S. application Ser. No. 09/394,018, filed Sep. 10, 1999, now U.S.Pat. No. 6,768,791, which is a Continuation-In-Part application of U.S.application Ser. No. 09/361,842, filed Jul. 27, 1999, now U.S. Pat. No.6,819,749, which claims the benefit of U.S. provisional application Ser.No. 60/128,874, filed Apr. 12, 1999. The present application also claimsthe benefit of U.S. provisional applications Ser. No. 60/167,572, filedNov. 26, 1999. All above-mentioned applications are hereby fullyincorporated by reference in the present application.

FIELD OF THE INVENTION

The present invention relates generally to communication systems. Moreparticularly, the present invention relates to speeding up the connecttime between communication systems.

BACKGROUND OF THE INVENTION

56 kbps modems are now standardized in accordance with the ITU V.90Recommendation. However, many 56 kbps modems, particularly end usermodems, may only be compatible with legacy modes such as K56flex, V.34,V.FC, and V.32. Such legacy modems, and downwardly compatible V.90modems, may have an undesirably long connect or initialization timebetween dial-up and full rate data mode. The startup time can be up to30 seconds, which can be rather annoying and unattractive from theperspective of the end user, especially in light of other datacommunication protocols that appear to operate in an “always connected”manner.

V.90 modems that support legacy modem protocols typically perform thefunctions shown in Table 1 during initialization. The time periodsassociated with the operations set forth in Table 1 may vary fromconnection to connection depending upon various factors such as theserver speed and channel conditions.

TABLE 1 Conventional V.90 Modem Startup PROTOCOL OPERATION TIME(seconds) — Dialing 1 — Call Establishment 1 V.8bis Capabilities 3.5Exchange V.8 Capabilities 3.5 Exchange V.90 Phase 2 Probing & Ranging1.5 V.90 Phase 3 Digital Impairment 8.5 Learning; Initial APCM TrainingV.90 Phase 4 Final APCM 2.5 Training; Set Power Levels; ConstellationTransmission V.42/V.42bis Error Correction; 0.5 Data Compression — Login0.5-5 TOTAL = 22.5-27.0

The V.8bis operation includes a relatively long timeout period thatencompasses much of the time period associated with the operation. Thisoperation is described in detail in ITU-T Recommendation V.8bis(International Telecommunication Union, August 1996), the content ofwhich is incorporated by reference herein. The V.8bis protocol is anextension of the V.8 protocol, as described in ITU-T Recommendation V.8(International Telecommunication Union, February 1998), the content ofwhich is incorporated by reference herein. In accordance with V.8bisand/or V.8, the two modem devices exchange their individual capabilitiessuch that compatible protocols may be utilized during subsequentinitialization and data communication procedures.

The various V.90 startup phases are utilized to determine the analog anddigital channel characteristics, to train the modem equalizers, and tootherwise attempt to optimize the current communication session. Thedetails of the V.90 startup phases and other aspects of a V.90 modemsystem may be found in ITU-T Recommendation V.90 (InternationalTelecommunication Union, September 1998), the content of which isincorporated by reference herein. Although a portion of the V.90 startupsegments shown in Table 1 are required without regard to the location orstatus of the client modem, many of the operations could be eliminatedor shortened upon repeated connections associated with the same (ornearly identical) channel characteristics.

In a conventional V.90 modem system, error correction and datacompression techniques are performed during the V.42/V.42bis stage. Thespecifics of V.42 are contained in ITU-T Recommendation V.42(International Telecommunication Union, October 1996), the content ofwhich is incorporated by reference herein. The specifics of V.42bis arecontained in ITU-T Recommendation V.42bis (InternationalTelecommunication Union, January 1990), the content of which isincorporated by reference herein. The V.42 operation is desirable suchthat the modem system can perform the login procedure in a substantially“error free” mode. The login procedure may be conducted with CHAP andPAP protocols; both are utilized for security purposes in the context ofpoint-to-point protocol (“PPP”) connections, e.g., a connection betweena client computer and an internet service provider server. From theperspective of the V.90 modem devices, the login information istransmitted as data. Once the login procedure is performed, the dial-upconnection is complete and data may be transmitted between the serverand the host software associated with the client.

The widespread use of the internet as a daily research, entertainment,and communication tool has increased the deployment of 56 kbps modems.However, many channels can only support legacy modes such as V.34. Thus,although most newer modems (particularly those sold with new personalcomputers) are compatible with the V.90 Recommendation, many legacymodes are still in use. The long initialization period associated withV.90 modems that fall back into legacy modes may be annoying andundesirable in many applications and can be a serious hindrance where auser would like to establish an immediate connection after anunanticipated disconnect. In addition, even in the context of aconnection between two V.90 modem devices, the long V.90 startup phasesmay test the mettle of an impatient end user. Accordingly, it would behighly desirable to reduce the initialization time normally associatedwith a conventional V.90 modem system.

A given modem communication session may be interrupted or disconnectedfor any number of reasons. For example, a call waiting signal maydisrupt a modem connection to the extent that the modem call must eitherbe reconnected or reinitialized. As another example, it may be possibleto place a current modem connection on hold to enable the user to answeran incoming call in response to a call waiting signal or to enable theuser to place an outgoing call without disconnecting the modemconnection. Ideally, the modem connection could be re-established in aninstantaneous manner. However, in a practical system, a retraining orreinitialization procedure must be carried out to ensure that the twoend devices are properly synchronized and to ensure that the channel isadequately equalized. As discussed above, conventional V.90 modemsystems may spend more than 20 seconds during such retraining andreinitialization. Accordingly, it would also be desirable to reduce thereconnection time between the same modem devices in response to atemporary disconnect or a temporary pause in the data communication.

One major time consuming portion of modem training and negotiationoccurs during parameter exchanges, such as exchange of data signalingrate, preceding coefficient, spectral shaping, constellation informationand etc. With reference to FIG. 5, it is shown that, for example, duringV.90 negotiations, an analog pulse code modulation (“APCM”) modem 580transmits a constellation parameter (“CP”) frame 510 to a digital pulsecode modulation (“DPSM”) modem 590 that, in exchange, transmits amodulation parameter (“MP”) frame 520 to the APCM modem 580. The MPframe 520 and the CP frame 510 are in synchronous form and include manybits of information and CRC information for error checking purposes (seeFIGS. 17 and 18), as further described below.

As shown in FIG. 5, the APCM modem 580 continuously transmits CP frames510 to the DPCM modem 590 until the APCM modem 580 receives a receiptacknowledgement from the DPCM modem 590 for one of the transmitted CPframes 510. Similarly, the DPCM modem 590 continuously transmits MPframes 520 to the APCM modem 580 until the DPCM modem 590 receives areceipt acknowledgement from the APCM modem 580 for one of thetransmitted MP frames 520.

The receipt acknowledgement for the CP frame 510 is transmitted in theform of an MP frame 520, including each and every bit of information andhaving the acknowledgement bit 33 of the MP frame 520 set to a “1”. TheMP frame 520 having its acknowledgement bit 33 set to a “1” is denotedas MP′ frame 522. Once the DPCM modem 590 receives a CP frame 510, theDPCM modem 590 starts transmitting the MP′ frames 522 instead of the MPframes 520. This repeated transmission of MP′ frames 522 continues untilthe DPCM modem 590 receives a receipt acknowledgement for the MP or MP′frames 520 or 522.

Similar to the DPCM modem 590, the receipt acknowledgement from the APCMmodem 580 is transmitted in the form of a CP frame 510, including eachand every bit of information and having the acknowledgement bit 33 ofthe CP frame 510 set to a “1”. The CP frame 510 having itsacknowledgement bit 33 set to a “1” is denoted as CP′ frame 512. Oncethe APCM modem 580 receives an MP frame 520, the APCM modem 580 startstransmitting the CP′ frames 512 instead of the CP frames 510. Thisrepeated transmission of CP′ frames 512 continues until the APCM modem580 receives a receipt acknowledgement for the CP or CP′ frames 510 or512.

The repeated transmissions of these long CP, CP′, MP and MP′ frames,including many bits of information, are indeed a tremendous overhead.This problem, however, gets even more exuberated in the next generationof standards, such as the ITU V.92 Recommendation, as more parametersand bits of information must be exchanged between the modems. FIG. 19shows an example of the V.92 constellation parameter frame for the APCMmodem 580 referred to as CPa frame 1900. As seen, the CPa frame includesmany more bits of information than the CP and MP frames 1800 and 1900(see FIGS. 17, 18 and 19), such as the constellation information withhigh resolution as well as precoder and prefilter coefficients. The CPaframe 1900 further includes variable length parameters, such asparameter 1920, that can potentially add many more bits of informationto the CPa frame 1900.

Concerns have been raised that because of the acknowledgement mechanismintroduced in the ITU Recommendation V.34 and re-used in the ITURecommendation V.90, the startup time may be unduly increased for theITU Recommendation V.92, due to these long sequences. For example,during a V.92 PCM upstream startup, a significant amount of informationneeds to be exchanged between the DPCM modem 590 and the APCM modems580. In particular, the DPCM modem 590 needs to transmit very longsequences, including constellation information with high resolution aswell as precoder and prefilter coefficients in the CPa frames.

Accordingly, there is an intense need in the art to eliminate thetremendous overhead of repeatedly transmitting these very longsequences, including many parameters and bits of information, therebyreducing the training and negotiation time and achieving a quickconnect.

SUMMARY OF THE INVENTION

The present invention provides techniques to shorten the startup andreconnection times associated with a data communication system thatemploys a modem. The quick reconnect technique leverages the knownchannel characteristics of a previous connection to reduce thereinitialization period associated with subsequent attempts to reconnectthe same two modem devices. In accordance with one illustrativeembodiment, the techniques of the present invention are utilized toreduce the reconnection time for a communication session that follows anupper layer protocol, e.g., PPP. Although not limited to any specificmodem application, the quick startup and reconnect procedures may beused to eliminate portions of the initialization protocols or processesnormally employed by a V.90 modem, e.g., V.8bis, V.8, digital impairmentlearning, initial training, probing and ranging, or the like. Inaddition, the quick startup and reconnect techniques may perform certainoperations at a different time or in a different order in comparison toa conventional modem startup technique.

The above and other aspects of the present invention may be carried outin one form by a method for reducing the reconnection time associatedwith a data transmission system having a first device configured tocommunicate with a second device over a communication channel. Theillustrative method involves establishing a communication sessionbetween the first device and the second device over the communicationchannel, obtaining a number of operating parameters for the datatransmission system, where the operating parameters are associated withthe communication channel, and storing at least one of the operatingparameters at the second device. After a temporary pause in thecommunication session, the operating parameters are recalled at thesecond device.

According to one aspect of the present invention, during the startup,retrain, renegotiation, quick connect or other handshaking processesbetween the communication systems, the communication systems exchange anumber of parameters such as modulation, constellation, precoder,prefilter and other communication related information. The communicationsystems exchange one long information sequence including all necessaryparameters or communication information. Subsequently, the communicationsystems start transmitting short sequences, including an acknowledgementinformation portion, but not all the other parameters or informationembedded in the long sequences. Once each communication system receivesa short sequence with the acknowledgment information indicating receiptof the long information sequence, the communication systems may move onto the next stage of the handshaking process. The use of shortinformation sequences substantially shortens the handshaking process andeliminates the delay and overhead introduced by continuous transmissionsand retransmissions of the long information sequences.

In yet another aspect of the present invention, if one of thecommunication systems does not receive an acknowledgement sequencewithin a predetermined time or event, that communication system mayretransmit another long information sequence. Subsequently, theretransmitting communication system may continue transmitting the longinformation sequences or may start transmitting the short sequences onceagain.

These and other aspects of the present invention will become apparentwith further reference to the drawings and specification, which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived byreferring to the detailed description and claims when considered inconnection with the Figures, where like reference numbers refer tosimilar elements throughout the Figures, and:

FIG. 1 is a block diagram depicting a general modem system environmentcapable of supporting point-to-point protocol (“PPP”) connections;

FIG. 2 is a flow diagram of a general quick startup process according tothe present invention;

FIG. 3 is a block diagram depicting an illustrative modem systemconfigured in accordance with the present invention;

FIG. 4 is a flow diagram illustrating portions of a quick startupprocess performed by two modem devices;

FIG. 5 is a timing diagram corresponding to a quick startup processperformed by two modem devices;

FIG. 6 is a timing diagram corresponding to a quick reconnect processperformed by two modem devices;

FIG. 7 is a flow diagram illustrating a quick reconnect processperformed by two modem devices;

FIGS. 8-15 are timing diagrams corresponding to different modem-on-hold,reconnect, and clear down situations;

FIG. 16 is a block diagram of a modem system environment in whichvarious aspects of the present invention may be incorporated;

FIG. 17 illustrates the definition of bits in an example modulationparameter (MP) frame;

FIG. 18 illustrates the definition of bits in an example constellationparameter (CP) frame;

FIG. 19 illustrates the definition of bits in an example constellationparameter for analog modem (CPa) frame;

FIG. 20 illustrates the definition of bits in an example shortmodulation parameter (MPs) frame;

FIG. 21 illustrates the definition of bits in an example shortconstellation parameter (CPs) frame;

FIG. 22 illustrates the definition of bits in an example shortconstellation parameter for analog modem (CPas) frame;

FIG. 23 illustrates an example of exchange of conventional modulationparameter (MP) frames according to the ITU V.34 Recommendation;

FIG. 24 a illustrates an example of quick exchange of modulationparameter (MP) frames according to one embodiment of the presentinvention;

FIG. 24 b illustrates an example of quick exchange of modulationparameter (MP) frames and constellation parameter (CP) frames accordingto one embodiment of the present invention;

FIG. 24 c illustrates an example of quick exchange of constellationparameter (CP) frames and constellation parameter frames for the analogmodem (CPa) according to one embodiment of the present invention;

FIG. 25 a illustrates an example of quick exchange of modulationparameter (MP) frames in case of an erroneous frame transmissionaccording to one embodiment of the present invention;

FIG. 25 b illustrates an example of quick exchange of modulationparameter (MP) frame and constellation parameter (CP) frame in case ofan erroneous frame transmission according to one embodiment of thepresent invention;

FIG. 25 c illustrates an example of quick exchange of constellationparameter (CP) frame and constellation parameter frame for the analogmodem (CPa) in case of an erroneous frame transmission according to oneembodiment of the present invention;

FIG. 26 illustrates an example of a rate renegotiation process occurringbetween the APCM and DPCM modems according to one embodiment of thepresent invention;

FIG. 27 illustrates an example of a fast train process occurring betweenthe APCM and DPCM modems according to one embodiment of the presentinvention; and

FIG. 28 illustrates an example of a quick connect training processoccurring between the APCM and DPCM modems according to one embodimentof the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention may be described herein in terms of functionalblock components and various processing steps. It should be appreciatedthat such functional blocks may be realized by any number of hardwarecomponents configured to perform the specified functions. For example,the present invention may employ various integrated circuit components,e.g., memory elements, digital signal processing elements, logicelements, look-up tables, and the like, which may carry out a variety offunctions under the control of one or more microprocessors or othercontrol devices. In addition, those skilled in the art will appreciatethat the present invention may be practiced in any number of datacommunication contexts and that the modem system described herein ismerely one illustrative application for the invention. Further, itshould be noted that the present invention may employ any number ofconventional techniques for data transmission, signaling, signalprocessing and conditioning, and the like. Such general techniques thatmay be known to those skilled in the art are not described in detailherein.

It should be appreciated that the particular implementations shown anddescribed herein are merely exemplary and are not intended to limit thescope of the present invention in any way. Indeed, for the sake ofbrevity, conventional encoding and decoding, timing recovery, automaticgain control (“AGC”), synchronization, training, and other functionalaspects of the data communication system (and components of theindividual operating components of the system) may not be described indetail herein. Furthermore, the connecting lines shown in the variousfigures contained herein are intended to represent exemplary functionalrelationships and/or physical couplings between the various elements. Itshould be noted that many alternative or additional functionalrelationships or physical connections may be present in a practicalcommunication system.

FIG. 1 is a block diagram depicting a general modem system 100 in whichthe techniques of the present invention may be practiced. For purposesof this description, modem system 100 is assumed to be capable ofsupporting connections associated with an upper layer protocol, e.g.,point-to-point protocol (“PPP”) connections. PPP connections aretypically associated with internet communications between, e.g., anindividual end user and an internet service provider. In this respect,modem system 100 includes a plurality of server modems (identified byreference numbers 102 a, 102 b, and 102 n) and a client modem 104.Server modems 102 may each be associated with an internet serviceprovider or any suitable data source. Client modem 104 may be associatedwith a suitable data source, e.g., a personal computer capable ofrunning host software 105. For purposes of this description, hostsoftware 105 may be an operating system such as MICROSOFT WINDOWS, orany application program capable of functioning in conjunction with modemsystem 100. Although not shown in FIG. 1, client modem 104 may beintegrated with the personal computer.

In the context of this description, modem system 100 may employ 56 kbpsmodems that are compatible with the V.90 Recommendation, legacy 56 kbpsprotocols, the V.34 Recommendation, or the like. Although the presentinvention is described herein in the context of a V.90 modem system, thetechniques can be equivalently applied in a V.34 modem system or in anynumber of legacy modem systems. V.90 or 56 kbps modem devices aresuitable for use in modem system 100 where a given server modem 102utilizes a digital connection 106 to the digital telephone network 108.The client modem 104 is connected to a local central office 110 via ananalog local loop 112. Thus, the communication channel establishedbetween client modem 104 and any server modem 102 is digital up to thecentral office 110. Thereafter, the digital signals are converted to ananalog signal for transmission over the local loop 112.

If an end user desires to establish an internet connection, hostsoftware 105 may perform any number of operations in response to a usercommand. For example, host software 105 may prompt client modem 104 todial the telephone number associated with server modem 102 a (which, forthis example, is the server modem associated with the user's internetservice provider). Server modem 102 a and client modem 104 perform ahandshaking routine that initializes the equalizers, echo cancelers,transmit power levels, data rate, and possibly other operationalparameters associated with the current communication channel. Inaddition, host software 105 may cause client modem 104 to transmit andreceive authentication data that enables the user to log onto theinternet via the service provider. As mentioned above, theauthentication data may be exchanged between server modem 102 a andclient modem 104 in accordance with the known CHAP or PAP techniques. Inan alternate embodiment that employs a non-PPP upper layer protocol, asuitable login procedure may be conducted instead of the CHAP or PAPprocedures.

As discussed previously, the dial-up connection time (and reconnectiontime) associated with conventional modem systems may be undesirablylong. The present invention takes advantage of the repeated use of acommunication channel between modem devices, e.g., the communicationchannel that is established between server modem 102 a and client modem104. Assuming that client modem 104 is associated with a desktoppersonal computer resident at a specific location, the connection to anygiven server modem 102 will necessarily be established over the sameanalog communication channel. In other words, client modem 104 willalways establish an analog channel between the user premises and centraloffice 110. Disregarding slight variations in the analog channel due totemperature and other environmental effects, the initialization ofclient modem 104 (with respect to the analog channel) will remainsubstantially constant from connection to connection.

FIG. 2 is a flow diagram of a general quick startup process 200 that maybe performed by a data communication system such as modem system 100. Ina practical system, process 200 may be cooperatively performed by servermodem 102, client modem 104, host software 105, and/or any functionalcomponent of modem system 100. In addition, process 200 may be realizedin the context of an overall initialization procedure that follows anynumber of conventional modem protocols.

Quick startup process 200 may begin with a task 202, which relates tothe establishment of a call between client modem 104 and a server modem102. In the context of this example, client modem 104 is considered tobe the calling device. Accordingly, host software 105 and/or clientmodem 104 dials the telephone number associated with, e.g., server modem102 b. Assuming that server modem 102 b is capable of making anadditional connection, it will go off hook and generate a suitableanswer tone in a conventional manner. When both modem devices are offhook and communicating with each other, a communication channel isestablished via digital connection 106, telephone network 108, centraloffice 110, and analog local loop 112. The dialing, ringing, andanswering procedures utilized during task 202 may follow conventionalprotocols.

Following task 202, a query task 204 may be performed by modem system100 to ascertain whether a quick connect protocol is supported. Querytask 204 may be necessary to enable different server modems anddifferent client modems to be interoperable and compatible. For example,server modem 102 b may be a V.90 modem device that supports the quickconnect features of the present invention, while client modem 104 may bea legacy 56 kbps modem device that does not support the quick connectfeatures. Portions of query task 204 may be performed by server modem102 b or client modem 104. An illustrative technique for performingquery task 204 is described in detail below. Task 204 may beequivalently performed when client modem 104 initiates the call or whenserver modem 102 initiates the call.

If query task 204 determines that the quick connect protocol is notsupported by both modem devices, then a task 206 may follow. Task 206prompts modem system 100 to begin a conventional initialization routine.For example, in the context of a V.34 or V.90 modem system, task 206 maybegin a capabilities exchange protocol such as V.8bis. Alternatively,some modem systems may only implement the V.8 capabilities exchangeprotocol. Older legacy modem systems may skip the V.8 and V.8bisprocedures altogether and perform an appropriate initialization routineaccording to the legacy mode. Following task 206, modem system 100 mayconduct a known startup procedure in accordance with an applicable modemspecification. For example, if modem system 100 supports V.90, then task208 may be associated with conventional V.90 equalizer training, echocanceler training, constellation design, power level verification, andother startup operations. If tasks 206 and 208 are performed, then thestartup time associated with the communication session is essentiallythe same as the startup time for a conventional V.90 connection.

If query task 204 determines that the quick connect protocol is fullysupported, then a query task 210 may also be performed. Query task 210tests whether the characteristics of the established communicationchannel are similar to corresponding characteristics of a previouslyestablished communication channel. Briefly, query task 210 compares oneor more attributes of a received sequence to stored attributes of apreviously received sequence associated with the previously establishedchannel. The received signal conveys information regarding thecharacteristics of the communication channel. In particular, thereceived signal conveys information relative to analog local loop 112.

In the illustrative embodiment described herein, where one modem deviceis connected digitally to the digital telephone network 108, analoglocal loop 112 affects signals in a substantially consistent manner fromconnection to connection. Although the analog characteristics will besimilar for repeated connections to the same server modem 102, slightvariations in temperature, humidity, other environmental changes,physical changes in the system hardware, and other operationalparameters contribute to random fluctuations in the current channelcharacteristics used for comparison purposes. Nonetheless, thecomparison procedure performed during query task 210 is preferablydesigned to accommodate such fluctuations. For purposes of thisdescription, “similar” characteristics means that query task 210 willassume that the current channel matches a previous channelnotwithstanding normal variations due to the uncontrollable andunpredictable factors mentioned above.

If query task 210 determines that the parameters of the currentcommunication channel do not match the parameters of a previouscommunication channel, then a task 212 may be performed. Task 212, liketask 206, prompts modem system 100 to begin a conventionalinitialization routine. In a preferred embodiment, if modem system 100verifies that the quick connect protocol is fully supported (query task204), then most, if not all, of the V.8bis procedure may be skipped.Accordingly, the V.8 capabilities exchange protocol may be prompted bytask 212. Thereafter, a task 214 may be performed to cause modem system100 to enter the conventional V.90 startup procedure. Task 214 issimilar to task 208 described above. If tasks 212 and 214 are performed,then the startup time associated with the communication session may bereduced by approximately three seconds, which is the typical time periodrequired to conduct the V.8bis procedures. Accordingly, even if querytask 210 determines that the current channel is not similar to aprevious channel, quick startup process 200 reduces the overallinitialization time of modem system 100.

If query task 210 finds that the current channel characteristics “match”the stored characteristics of a previously established channel, then atask 216 may be performed. An abbreviated training procedure isconducted during task 216. As described in more detail below, modemsystem 100 leverages the known characteristics of the current channelsuch that the modem devices can be immediately trained. For example,although the specific timing phase of digital impairments (e.g., robbedbit signaling) may be unknown, the types of digital impairments will beconsistent for repeated connections. Thus, in the context of a V.90modem system, the lengthy digital impairment learning procedure need notbe fully implemented. In addition, the initial training of equalizersand echo cancelers, and the initial determination of PCM codec transmitlevels and data rates need not be performed.

A task 218 may be performed to enable modem system 100 to operate at aninitial data rate. It should be appreciated that portions of thetraining associated with task 216 may be performed at the initial datarate associated with task 218. Modem system 100 is able to quicklyoperate at the initial data rate by recalling the initializationparameters associated with the previously stored channel. During task218, modem system 100 may perform final training of the equalizers andecho cancelers, exchange modulation parameters, and exchangeconstellation signal points for use during the full rate data mode. Inaccordance with the present invention, PPP data may be transmittedduring task 218 in connection with one or more final training sequences.For example, the PPP data may be associated with the exchange of log-inauthentication information, e.g., CHAP or PAP information. In view ofthe transmission of data during task 218, this portion of quick startupprocess 200 may be considered to be a first data mode or a data phaseone.

Following task 218, quick startup process 200 causes modem system 100 tooperate at a final data rate (task 220). In the context of thisembodiment, this portion of process 200 may be considered to be a seconddata mode or a data phase two. The transition between the initial andfinal data rates preferably occurs in a seamless manner; modem system100 employs a suitable signal timing or synchronization technique toenable such a data rate transition. During the full data mode, modemsystem 100 utilizes the signal point constellation exchanged during task218. Once modem system enters the final data mode, quick startup process200 ends.

FIG. 3 is a block diagram depicting an illustrative modem system 300configured in accordance with the present invention. Modem system 300 ispreferably configured to carry out quick startup process 200 and otherprocesses described herein. By way of example, modem system 300 isdescribed herein in the context of a 56 kbps or V.90 system (or a systemsubstantially similar to a V.90 system). However, it should beappreciated that the particular implementation shown in FIG. 3 is notintended to limit the scope of the present invention in any way.

Generally, modem system 300 includes a first modem, e.g., modem 302, anda second modem, e.g., modem 304. In the context of this description,modem 302 is considered to be a server modem and modem 304 is consideredto be a client modem (see FIG. 1). It should be appreciated that modems302 and 304 may be similarly configured such that both can function ineither a transmit or receive mode. Modems 302 and 304 are generallyconfigured in accordance with known principles to communicate over atelecommunication network, such as the public switched telephone network(“PSTN”) 306, via at least one communication channel (e.g., channels 308and 310). For purposes of this description, modem 302 is connecteddigitally to PSTN 306 while modem 304 is connected to PSTN via a centraloffice (not shown) and an analog local loop, as described above inconnection with FIG. 1. For the sake of clarity, FIG. 3 does not showthe various encoder, decoder, and other functional elements that wouldtypically be present in a practical modem system.

Modem 302 may include a processor element 312, while modem 304 mayinclude a processor element 314. In addition to the specific operationsdescribed herein, processors 312 and 314 are suitably configured tocarry out various tasks associated with the operation of modem system300. Indeed, modem system 300 may incorporate any number of processors,control elements, and memory elements as necessary to support itsfunctionality. Such processor, control, and memory elements may suitablyinteract with other functional components of modems 302 and 304 tothereby access and manipulate data or monitor and regulate the operationof modem system 300.

Processor 312 may be operatively associated with a quick connectconfirmation routine, which is illustrated as a functional block 322.Quick connect confirmation routine 322 may be employed during query task204 (see FIG. 2). Processor 312 is also operatively associated with anumber of training routines 324. Training routines 324 may be utilizedfor initial and/or final training of modem system 300. Training routines324 may be employed during task 216, as described above. Processor 312may also operate in conjunction with a dial-up authentication scheme326, e.g., information exchanging in accordance with PAP or CHAP. TheCHAP/PAP functionality may be alternatively (or additionally) realizedin one or more software applications maintained by the servercorresponding to modem 302. These illustrative operations are notintended to limit the applicability of processing element 312, which ispreferably configured to support any number of additional operations.

Modem 302 includes a transmitter 316, which is configured to transmitencoded symbols in accordance with conventional data transmissiontechniques. Such symbols may represent data, training sequences,synchronization signals, control signals, information exchangesequences, and any suitable communication signal utilized by modemsystem 300. Modem 302 also includes a receiver 318, which may beconfigured in accordance with any number of known modem technologies.Receiver 318 is configured to receive communication signals from modem304; such signals may include encoded information bits, control signals,information exchange sequences, training sequences, and the like.Receiver 318 may include or be functionally associated with an equalizerstructure 317 and an echo canceler structure 319. The configuration andoperation of equalizer structure 317 and echo canceler structure 319 maybe consistent with any number of conventional techniques, e.g., adaptivefiltering algorithms.

Modem 302 is preferably configured to generate, process, and transmitdifferent data and signals associated with the operation of modem system300. Such data, signals, and sequences may be suitably stored,formatted, and produced by any number of microprocessor-controlledcomponents. For illustrative purposes, FIG. 3 depicts a number of blocksrelated to different operational features of modem system 300; suchoperational features may have specific data sequences, control signals,or the like, associated therewith. Although a practical system mayprocess and transmit any amount of additional or alternative data, theparticular embodiment described herein functions in cooperation with atleast the following types of data: a transition sequence 328, an answersignal point sequence 330, authentication information 332, a quickconnect identifier 334, training information 336, and user data 338.This data, and the handling of the data by modem system 300, isdescribed in detail below.

Modem 302 also includes a suitable amount of memory 320 necessary tosupport its operation. Memory element 320 may be a random access memory,a read only memory, or a combination thereof. Memory element 320 may beconfigured to store information utilized by modem system 300 inconnection with one or more processes related to the present invention.For example, memory element 320 may be configured to store a suitableanswer signal point sequence 338. Memory 320 may store specific signalpoints, transmit levels, a pattern utilized to format a sequence fortransmission, or the like. In the preferred embodiment, answer signalpoint sequence 338 corresponds to sequence 330 (described above). Memoryelement 320 may also be configured to store a number of parametersrelated to the training of receiver 318. These receiver parameters,which are depicted as block 340, may be associated with theinitialization of equalizer structure 317 and/or echo canceler structure319. As a practical matter, memory element 320 may store informationrelated to the analog and/or digital characteristics, e.g., filter tapcoefficients, of equalizer structure 317 and echo canceler structure319, and transmit codec level estimates.

In accordance with a preferred embodiment of the present invention,memory element 320 is also capable of storing a number of parameters,attributes, and/or characteristics of a previously established channel(illustrated as a previous channel block 342). The previous channelparameters 342 may be stored at any suitable time during a communicationsession or periodically updated during a session. Indeed, modem 302 andmodem 304 may both be configured to save the current channel parametersto anticipate a temporary interruption, delay, or disconnectionassociated with the current communication session (whether suchinterruption, delay, or disconnection is intentional or unintentional).As described in more detail below, in response to a temporarydisconnection or pause in the modem data transmission mode, modem 302can be placed “on hold” until the communication session is to bereinitiated. At that time, modems 302 and 304 may access the storedchannel parameters rather than conduct a lengthy retrain procedure.

Modem 304 includes a receiver 350, which is operatively associated withan equalizer structure 352 and an echo canceler structure 354. Receiver350 is configured to receive communication signals from modem 302. Modem304 also includes a transmitter 356 configured to transmit communicationsignals to modem 302. These components of modem 304 may be similar tothe corresponding components of modem 302. Thus, for the sake ofbrevity, the description of features and functions that are common tomodems 302 and 304 will not be repeated in this description of modem304.

Processor 314 may be operatively associated with a quick connectconfirmation routine 358, one or more training routines 360, and adial-up authentication scheme 362. These processing functions aresimilar to the corresponding functions described above in connectionwith processor 312. In addition to these features, processor 314 may beoperatively associated with a digital impairment learning routine 364.Digital impairment learning routine 364 may be compatible with thedigital impairment learning procedure carried out by conventional V.90modems. Routine 364 may be utilized to enable modem 304 to analyze adigital impairment learning sequence transmitted by modem 302 and todetermine the types of digital impairments present in the communicationchannel and any timing phases associated with such digital impairments.Routine 364 may interact with a memory element 366 such that modem 304can store the digital impairment profile associated with a givencommunication channel. Routine 364 may enable modem 304 to selectappropriate signal points (or a signal point) that function toilluminate or highlight robbed bit signaling present in the channel. Forexample, if modem 304 determines that the network forces robbed bits(typically the least significant bit of a symbol) to zeros, then asignal point having a least significant bit of one may be selected suchthat the robbed bit signaling phases can be easily detected.

Processor 314 may also be configured to conduct a channel comparisonroutine 368, which may be performed during task 210 described above inconnection with FIG. 2. Channel comparison routine 368 preferablydetermines whether the characteristics of the current communicationchannel are similar to stored characteristics associated with apreviously established communication channel. In the context of thisdescription, the current channel is a repeated connection of thepreviously established channel, and a number of stored characteristicsmay be resident in memory element 366. Routine 368 is described in moredetail below.

As with processor 312, the illustrative operations set forth herein arenot intended to limit the applicability of processing element 314, whichis preferably configured to support any number of additional operations.

Like modem 302, modem 304 is configured to generate, process, andtransmit different data and signals associated with the operation ofmodem system 300. Such data, signals, and sequences may be suitablystored, formatted, and produced by any number ofmicroprocessor-controlled components. Although a practical system mayprocess and transmit any amount of additional or alternative data,transmitter section 356 is illustrated in conjunction with the followingtypes of data: a quick connect identifier 370, a transition sequencesignal point identifier 372, training information 374, authenticationinformation 376, and user data 378. This data, and the handling of thedata by modem system 300, is described in detail below.

As mentioned above, modem 304 includes a suitable amount of memory 366necessary to support its operation. Memory element 366 is similar tomemory element 320. In the preferred embodiment, memory element 366 isconfigured to store an answer signal point sequence 380 that is relatedto the corresponding answer signal point sequence 338 utilized by modem302. In this embodiment, the same answer signal point sequence ispredetermined and known at both modems 302 and 304. Memory element 366may also store a number of parameters, attributes, and/orcharacteristics of a previously established channel (illustrated as aprevious channel block 382). The previous channel parameters 382 may bestored at any suitable time during a communication session orperiodically updated during a session. Like memory element 320, memoryelement 366 may also be configured to store a number of parameters 384related to the training of receiver 350. These stored receiverparameters 384 are preferably accessed by modem 304 to effectivelyreduce the startup latency typically experienced with conventional V.90modem systems.

A number of features of the present invention contribute to thereduction in conventional V.90 modem startup and/or reconnect times,e.g., the elimination or abbreviation of the V.8bis procedure, theelimination or abbreviation of the initial training procedure, and theexchanging of login authentication data earlier in the initializationprocess (rather than waiting until the full data rate is achieved). Inone embodiment, the login authentication data is exchanged while themodem system is in an initially trained mode associated with anintermediate data rate. Any one of these (and other) features of thepresent invention may be implemented in modem system 300.

FIG. 4 is a flow diagram illustrating portions of a quick startupprocess 400 performed by two modem devices, and FIG. 5 is a timingdiagram 500 corresponding to an illustrative quick startup processperformed by two modem devices. Timing diagram 500 includes acronyms andabbreviations that are often used in the context of V.8, V.8bis, V.34,V.90, and other data communication protocols. The use of suchterminology herein is intended to illustrate the concepts of the presentinvention in the context of one practical embodiment. However, thepresent invention may be employed in any suitable context, and thespecific signals, number of sequences, timing of the sequences, datarates, and interaction between the two modem devices shown in FIG. 5 arenot intended to limit the scope of the invention in any way.

Quick startup process 400 is depicted in a manner that indicates tasksassociated with a client modem, e.g., APCM, and a server modem, e.g.,DPCM. Similarly, timing diagram 500 shows the general sequencing ofsignals transmitted by an APCM and a DPCM. In FIG. 5, the arrows betweenthe two major sequences represent responses or interactions between theAPCM and the DPCM.

Quick startup process 400 may begin with a task 402, which causes theAPCM to dial the telephone number associated with the DPCM. As describedabove, the call will be established over local loop 112, central office110, and digital telephone network 108 (see FIG. 1). In response to theinitial ring tone, the DPCM may be placed in an off hook state (task404), i.e., the DPCM will answer the call. Of course, the APCM and theDPCM may be configured to place, answer, and process calls in accordancewith conventional telephony protocols. Following task 404, a task 406may be performed to initialize a capabilities exchange protocol such asV.8 or V.8bis. In the embodiment described herein, a capabilitiesrequest signal (represented by CRe in FIG. 5) may be transmitted duringtask 406. The CRe signal may function to inform the APCM that the DPCMsupports the quick connect procedure. The CRe signal may be a modifiedversion of the conventional V.8bis signaling tones, e.g., the V.8bistones may be amplitude modulated. Alternatively, the frequencyassociated with a signaling tone may be jittered in a periodic manner ora low-level wideband signal may be added to a tone. In this manner,legacy modem systems will recognize the CRe signal as the normal V.8bisCRe signal.

In response to the establishment of a call associated with the currentcommunication channel, the APCM may perform a task 408 to suitablytransmit a quick connect identifier (QC) to the DPCM. In the practicalembodiment described herein, the transmission of the quick connectidentifier may be prompted in response to the detection of the CResignal by the APCM. The QC signal is preferably designed such thatlegacy modems and modems that do not support the quick connect protocolare not adversely affected by the QC signal, i.e., the QC signal shouldbe ignored by non-compatible devices. (If the APCM does not support thequick connect techniques described herein, then it will not generate theQC signal and the startup will proceed in a conventional manner, asdescribed above in connection with FIG. 2). In a preferred embodiment,the QC signal also conveys a signal point identifier that identifiessignal points (or one point) for use by the DPCM in a transitionsequence (represented by QTS and QTS\ in FIG. 5), where the signalpoints function to highlight, illuminate, or make apparent the digitalimpairments present in the communication channel. Thus, the QC signalsequence performs a dual function.

Assuming that the DPCM also supports the quick connect methodology, itpreferably performs a task 410 in response to the reception of the QCsignal. In connection with task 410, the DPCM transmits a quick connectacknowledgment (represented by the QCA signal in FIG. 5). As describedabove in connection with FIG. 2, if the DPCM does not acknowledge the QCsignal, or if the APCM somehow fails to receive the QCA signal, then themodem system will proceed with a conventional startup procedure. Theformat, configuration, and processing of the QC and QCA signals may becarried out by the respective portions of the individual modems, asdescribed above in connection with modem system 300 (see FIG. 3).

If the DPCM and the APCM both support the quick connect technique, thenany number of initialization routines may be eliminated, modified, orabbreviated, depending upon the specific application. For example, inthe context of a V.90 compatible modem system, the transmission of theQC signal may inherently indicate that the APCM is V.90 compliant.Similarly, the transmission of the QCA signal may inherently indicatethat the DPCM is also V.90 compliant. Consequently, the modem system mayeliminate portions or the entirety of the normal capabilities exchangeprotocol or protocols, such as V.8 and/or V.8bis. This feature by itselfcan reduce the startup latency by as much as five seconds (for a typicalconnection).

It should be appreciated that the quick connect identification andverification scheme described above in connection with task 402 throughtask 410 can be equivalently applied when the DPCM initiates the call tothe APCM. Such a situation may arise when, in response to an initialcall or request from the APCM, the DPCM calls the APCM to establish thecommunication channel. In this situation, the APCM will transmit the CResignal, the DPCM will transmit the QC signal, and the APCM will transmitthe QCA signal. In contrast to the above description where the APCMinitiates the call, the APCM may transmit an additional signal orsequence to suitably identify the transition sequence signal points tothe DPCM (rather than embedding the signal points in the CRe or QCAsequences).

Following task 410, the DPCM may perform a task 412 to obtain the signalpoints (or point) for use in a transition (or synchronization) sequence.As discussed above, the QC signal preferably conveys information thatidentifies signal points that make the presence of robbed bit signalingeasily detectable by the APCM. The determination of the particularsignal points may be carried out by the APCM, as described above inconnection with the digital impairment learning procedure 364 (see FIG.3). This determination may be based on past analyses of the digitalimpairments associated with a previous connection over the same channel.Task 412 may be performed by processor 312 after the APCM receives theQC signal.

In response to task 412, a task 414 may be performed such that asuitable transition sequence is transmitted by the DPCM. In an exemplaryembodiment, the transition sequence includes positive and negativevalues of the signal points obtained in task 412. Accordingly, the DPCMmay utilize the signal points selected by the APCM and a suitable signpattern (which may be predetermined) to generate the transitionsequence. The transition sequence is configured and formatted such thatthe APCM, upon detecting the transmission sequence, can synchronizeitself to the subsequent signal or sequence transmitted by the DPCM. Inthis manner, the APCM receiver can obtain its timing from the transitionsequence. The transmission sequence may be of any predetermined lengthand have any predetermined sign pattern. For example, in the embodimentdepicted in FIG. 5, the transition sequence is represented by the quicktiming sequence (QTS) and QTS\ signals, where QTS represents a specificsignal point sequence and QTS\ is the same sequence having oppositesigns. In FIG. 5, the QTS sequence is repeated for 810 symbols while theQTS\ sequence is repeated for 30 symbols.

In accordance with one practical embodiment of the present invention,the QTS sequence is formatted such that the period of the QTS rootsequence and the period of the robbed bit signaling (“RBS”) associatedwith the network connection have no common denominator (other than one).For example, one suitable QTS root sequence is 0, +A, −A, +A, −A (whereA represents a signal point that highlights the presence of RBS. Thus,for the embodiment illustrated in FIG. 5, this QTS root sequence, whichhas a period of five, is repeated 162 times while the QTS\ sequenceincludes six repetitions of the root QTS sequence with inverted signs.

For the above example, where the RBS period is assumed to be six, thereceived transition sequence may be subjected to a 30-point discreteFourier transform (“DFT”) to obtain the timing phase of the DPCM. Inaddition, the presence of RBS will be revealed at certain discretefrequencies associated with the DFT result. In this manner, timing andRBS information can be extracted from the received transition sequence.In addition, the timing phase information is obtained independently fromthe RBS information.

The DPCM is preferably configured to transmit a specific signal pointsequence during a task 416. The signal point sequence may be consideredto be a modified answer tone, as that term is understood by thosefamiliar with modem protocols. In FIG. 5, this signal point sequence isrepresented by the ANSpcm signal. As depicted in FIG. 3, a predeterminedANSpcm sequence 338 may be stored in memory element 320 for transmissionby transmitter section 316. In a practical embodiment, the DPCMtransmits the ANSpcm signal following the transition sequence. This maybe desirable to enable the APCM to anticipate the signal point sequenceonce it detects the transition sequence. In other words, the detectionof the transition sequence by the APCM will indicate that the signalpoint sequence will follow.

In a preferred embodiment, the ANSpcm signal comprises a sequence ofpulse code modulation signal points or a sequence of signal pointsassociated with pulse code modulation signal points. For example, theANSpcm signal may be formatted as a sequence of mu-law or A-lawcodewords or a sequence of universal codewords (U-codes). The. APCM andthe DPCM are preferably configured such that the ANSpcm signal ispredetermined and known prior to the initiation of quick startup process400. In an alternate embodiment, a number of different ANSpcm signalsmay be suitably stored in lookup tables or the ANSpcm signal may bedesigned by one of the modem devices and communicated in a suitablemanner to the other modem device prior to task 416. For example, theANSpcm signal may be designed such that the presence of RBS can beeasily detected by the APCM by analyzing the received ANSpcm signal. Insuch an embodiment, it may not be necessary for the transition sequence(QTS and QTS\) to identify or highlight the RBS.

In the context of V.8, the answer tone is generated as an amplitudemodulated 2100 Hz tone. In contrast, the present invention utilizes theANSpcm signal to generate a tone (e.g., a 2100 Hz tone) in a digitalmanner using pulse code modulation signal points. In other words, theANSpcm signal is a digital representation of an analog signal. TheANSpcm signal is preferably constructed with known pulse code modulationpoints such that the ANSpcm signal may be used for purposes other than amere answer tone. In a preferred embodiment, the ANSpcm signal includesmany of the available pulse code modulation points associated with theparticular telephone network. This aspect of the ANSpcm signal isdesirable such that the ANSpcm signal may be used to determine oridentify the characteristics of the current communication channel,particularly digital pads. The use of a large number of the possiblecodewords ensures that the ANSpcm signal will detect digital pads thatmay merge two input levels into one output level. The ANSpcm signal isalso configured to provide a tone suitable for disabling the networkecho cancelers and disabling the network echo suppressors.

If the ANSpcm signal is defined using look-up tables, a practicalimplementation may be difficult where multiple transmit levels arecontemplated or required. For example, ITU-T Recommendation V.90 allowsthe DPCM to specify 32 different transmit levels. Storing a separatetable for each transmit level may thus lead to excessive memoryrequirements. Accordingly, in an alternate embodiment, a procedure maybe defined for mapping a plurality of codewords associated with onetransmit level into a corresponding plurality of codewords associatedwith the other transmit levels. For example, given a table of PCMcodewords defining the ANSpcm signal for a level of −0.5 dBm0, theprocedure may involve mapping each individual PCM codeword to itscorresponding PCM level, scaling that level according to the desiredtransmit level reduction, quantizing the resulting level back to theclosest PCM level, and converting to the corresponding PCM codeword.Thus a corresponding ANSpcm signal can be constructed using the samemechanism in both the DPCM transmitter and the APCM receiver, henceproducing the identical sequence of PCM codewords on each side. Notethat, in accordance with this embodiment, the quantizing rule should beexact in dealing with “ties” in the quantization, i.e., if two PCMlevels are equidistant from the scaled level. For example, the rule maydictate that, in case of a tie, the PCM level closer to zero isselected.

In accordance with yet another embodiment, the overall method ofdefining the ANSpcm signal could be based on a predetermined algorithmthat generates the sequence of PCM codewords representing the ANSpcmsignal. For example, the signal could be defined as a collection oftones, 2100 Hz being the strongest, where the tones have predefinedamplitudes and initial phases. The sum of the tones would then be scaledaccording to the desired transmit level, and the resulting signal wouldbe quantized to the closest PCM level, again using an exact quantizingrule in case of a tie. However, this method would also employ an exactdefinition of either the sine or cosine function, as well as how manybits were accumulated in summing the tones, to ensure that thecalculations proceed in a consistent manner at both ends such that theANSpcm signal can be properly detected.

As described above, the APCM anticipates the transmission of the ANSpcmsignal. The digital impairments and analog characteristics associatedwith the communication channel will affect the ANSpcm signal as it istransmitted from the DPCM to the APCM. A task 418 may be performed bythe APCM to obtain a received sequence that is related to the ANSpcmsignal point sequence. The APCM may then perform a task 420 to compare anumber of attributes of the received sequence with a number of storedattributes of a previously received sequence associated with apreviously established communication channel. In an illustrativeembodiment, the previously received sequence is a digital impairmentlearning (“DIL”) sequence, which is a line probing sequence. In thisrespect, task 420 determines whether a characteristic of the currentchannel is similar to a corresponding characteristic of a previouslyestablished channel. In a preferred embodiment, the channelcharacteristics compared in task 420 are related to the digitalimpairments in the channel. In other words, task 420 validates a currentdigital impairment channel profile with a stored digital impairmentchannel profile. Task 420 may be performed by a suitable processorelement of the APCM (see FIG. 3.).

During task 420, any measurable characteristic of the points/levels, anymeasurable characteristic of the received sequence as a whole, and/orany measurable signal or quantity associated with the points/levels maybe analyzed by the APCM. For example, any number of individual points orlevels contained in the received sequence may be compared tocorresponding points or levels stored at APCM (the stored points orlevels may be associated with a prior DIL procedure). If the receivedpoints/levels “match” the stored points/levels or if the differencesbetween the received and stored points/levels are within a certainthreshold, then the APCM may assume that the current channel attributesmatch the stored channel attributes (see query task 210 in FIG. 2).

The APCM may perform a procedure 421 to suitably obtain and save anumber of attributes or characteristics of a previously establishedconnection to the current channel. As described above, procedure 421 maycause the APCM to store the characteristics of the points/levelscontained in a received DIL sequence. These past values are thereafterused during task 420. In this respect, procedure 421 may update theprevious values with new DIL values after the comparison in task 420 iscompleted, e.g., in response to a subsequent DIL procedure associatedwith the current connection.

As described above in connection with FIG. 2, if task 420 determinesthat the channel characteristics do not sufficiently match, then themodem system may revert to a conventional V.90 startup procedure. FIG. 5illustrates that the APCM may fall back into the V.8 protocol andtransmit a conventional V.8 call menu (CM) message to the DPCM. Theconventional V.8 startup for the APCM then follows along a sequence 502.In response to the CM message, the DPCM generates a conventional V.8joint menu (JM) message and proceeds in accordance with the conventionalV.8 initialization (indicated by a sequence 504). For the sake ofillustration, quick startup process 400 assumes that task 420 determinesthat the current communication channel is similar to a previouslyestablished communication channel.

If the APCM validates the current channel characteristics with aprevious channel, then it may trigger a quick startup routine to furtherreduce the initialization time associated with the modem system.Alternatively, the DPCM may be configured to trigger the quick startuproutine. Accordingly, a task 422 may be performed, during which themodem system is initially trained. (For the sake of clarity and brevity,portions of task 422 and portions of the subsequent tasks may beperformed by both the APCM and the DPCM; quick startup process 400depicts such combined functionality in the context of single processtasks). Task 422 may cause the APCM and the DPCM to be initialized inresponse to a number of stored parameters associated with the previouslyestablished communication channel. As mentioned above, the storedparameters may be related to the initialization or training of theequalizers, echo cancelers, transmit power levels, initial signal pointconstellations, or the like. Task 422 may operate in conjunction withprocedure 421, which preferably functions to obtain and store theinitialization parameters associated with the previous connection. Inthis respect, procedure 421 may be suitably designed to periodicallysave such parameters during the normal data mode of the previousconnection, after a renegotiation process, or in response to anycondition or event associated with the previous communication session.Procedure 421 may also be configured such that erroneous settings orinitialization parameters are not inadvertently saved.

In the context of a typical V.90 connection, task 422 may be related toa two-point training phase. Using the previous parameters, the modemsystem may be able to skip or abbreviate the conventional V.90 Phase 2probing and ranging procedure and to skip or abbreviate the conventionalV.90 Phase 3 digital impairment learning and initial trainingprocedures. As shown in FIG. 5, the APCM and the DPCM may each transmittraining sequences (represented by the TRN1 signals) during task 422.These training signals may be utilized to adaptively adjust theequalizer and echo canceler filter taps and to otherwise facilitatetraining of the modem system. Thus, one of the most time consumingprocedures of a V.90 startup (the training of the APCM equalizer) can beperformed in an efficient manner that allows ample time for fine tuningand training.

In addition to the initial training that occurs during task 422, a task424 may be performed. During task 424, the modem system may conducterror correction and/or data compression protocols. In a conventionalV.90 modem system, the V.42 Recommendation is followed for purposes oferror correction and the V.42bis Recommendation is followed for purposesof data compression. For example, in a normal V.90 operating modeassociated with a PPP connection, the V.42 and V.42bis procedures areperformed after final training and before the CHAP/PAP authenticationprocedure. V.42 and V.42bis are performed prior to the CHAP/PAPprocedure because the CHAP/PAP procedure is better suited to an “errorfree” channel. In contrast to conventional V.90 systems, task 424 mayperform V.42bis during Phase 3 of the V.90 startup. The shifting ofV.42bis forward in the startup process contributes to the reduction inconnection time. In FIG. 5, the XID signal represents a modified versionof the conventional V.42 XID signal. For example, the XID signal mayutilize a subset of the XID parameters used to negotiate compression andthe like. Portions of the V.42bis procedure may also be conducted inconnection with various modified signal sequences shown in FIG. 5. Forexample, the CPt signal may represent the conventional V.90 CPt signalcombined with one or more V.42bis signals.

In the preferred embodiment, the V.42bis procedures are performed toprovide a substantially “error free” channel. Following task 424, aCONNECT message is issued to the host software. The CONNECT messageindicates that the modem system is ready to transmit data at an initialdata rate at this time. The CONNECT message may be formatted, generated,and transmitted in accordance with known techniques.

In response to the CONNECT message, the host software begins a“simultaneous” upper layer protocol login procedure, e.g., a CHAP or PAPprocedure (task 428). Task 428 may be initiated automatically by thehost software or in response to a user entry. The CHAP/PAP datatransmission occurs in conjunction with a final training process. In thepreferred embodiment, the APCM and the DPCM transmit the CHAP/PAPauthentication data as scrambled digital data over the communicationchannel. The scrambling of the authentication data enables the modemdevices to perform final training on the authentication data. In aconventional V.90 modem system, the final training signals are formattedas scrambled “ones”. The scrambled ones carry no information; the finaltraining signal is merely utilized as a spectrally white source. Thepresent invention leverages the final training signals to carry userdata while the modem devices complete the training process. AlthoughCHAP/PAP data is one preferred form of user data, the present inventionis not limited to the transmission or exchange of authentication data.In addition, the particular scrambling algorithm may vary fromapplication to application.

In FIG. 5, the dual function signals are represented by the TRN2A/PPPand TRN2D/PPP signals. In this respect, the receiver sections in themodem devices may be trained at an initial data rate during a first timeperiod, e.g., during a data phase one, such that they may seamlesslytransfer to operating at a final data rate during a subsequent timeperiod, e.g., during a data phase two. Furthermore, the PPP log-inprocedure can be performed at the initial data rate during the firsttime period rather than after the modem system has been fullyinitialized.

During the initial data rate period, a task 430 may be performed toenable the APCM and the DPCM to exchange constellation parameters andmodulation parameters (represented by the CP and MP signals in FIG. 5)in a suitable manner. Task 430 may be performed in a conventional V.90manner. These parameters may be utilized by the modem devices during thesubsequent data mode. After the training and authentication proceduresare completed, the modem system preferably transitions to a full datarate in a seamless manner. A task 432 may be performed to conduct datatransmission at the full data rate. This period may be referred to asthe data phase two. Once the modem system enters the full data mode,quick startup process 400 ends.

In contrast to the conventional V.90 modem startup summarized in Table1, a modem system according to the present invention may experience areduced startup latency, as set forth in Table 2 below. Notably, thestartup time summarized in Table 2 is approximately half of the startuptime summarized in Table 1. The considerable reduction in startuplatency would be desirable in many situations, particularly in thecontext of a PPP dial-up internet connection using V.90 or legacy 56kbps modem systems.

TABLE 2 Quick V.90 Modem Startup PROTOCOL OPERATION TIME (seconds) —Dialing 1 — Call Establishment 1 V.8bis (abbreviated) Capabilities 1Exchange — Modified Answer 1 Tone V.90 Phase 3 + Initial APCM Training;2.5 V.42/V.42bis Error Correction; Data Compression V.90 Phase 4 + FinalAPCM Training; 2-5 Login Set Power Levels; Constellation Transmission;Username & Password TOTAL = 8.5-11.5

The techniques of the present invention may be implemented in othercontexts to reduce the reinitialization time associated with reconnectsafter a line corrupting event or a channel interruption. For example,many telephone customers subscribe to call waiting, calleridentification, and other telephony services. However, such services maybe disabled or nonfunctional if the telephone line is being utilized fora modem connection. If call waiting is not disabled during a modemconnection, then the signal tones may interrupt the modem connection. Ifthe user decides to answer the waiting line, then the off-hook andon-hook flash may cause the modem system to retrain its receivers orprompt a full reconnect procedure.

Rather than perform a time consuming reconnect or retrain procedure, amodem system may be configured to utilize stored analog and digitalimpairment information, equalizer settings, power levels, echo cancelersettings, constellations, and the like. Such stored information can beused to immediately reset the modem system parameters if the channelconnection is interrupted by a call waiting procedure, by an off-hookcondition at an extension telephone device, by a caller identificationrequest, or by any channel corruption event, whether such event isplanned or unintentional. In this scenario, both the client modem andthe server modem may store the relevant system attributes, modemoperating parameters, channel characteristics, and/or networkcharacteristics.

In one practical example, in response to a call waiting tone, the clientmodem may signal the server to enter a standby mode. The server modemcan then switch into an FSK mode to suitably detect the Class 2 calleridentification information while the server idles. If the user wants toanswer the second call, then the client modem may periodically transmitstandby signals or heartbeat tones to the server to instruct the serverto continue holding. When the second call ends and the user desires tocommence the data call, the client modem would commence a quickreconnect handshaking protocol (described below). On the other hand, ifthe user wants to terminate the first call, then a clear down messagemay be sent (alternatively, the periodic hold signal may end).

The quick reconnect handshake causes the modem devices to recall thesaved parameters and attributes of the “held” channel and the savedoperating parameters associated with the modem devices, as describedbriefly above in connection with previous channel parameters 342 and382. With this technique, the modem system can be reconnected in amatter of seconds. Thus, the data mode user will not suffer the longreconnect penalty after handling an incoming call waiting or calleridentification signal. The data mode user, using call waiting in thisfashion, would be capable of accepting intermittent interruptionswithout noticeable delays associated with the modem connection.

This feature may be utilized to simulate an “always connected” mode withconventional PPP modem connections. For example, pertinent channelcompensation information may be periodically saved for a givenconnection between a client modem and a server modem. The client usermay answer incoming second line calls while pausing the data mode asdescribed above. In addition, the data mode may be gracefully terminatedif the client user initiates an outgoing voice call. After the voicecall terminates, the client modem may re-dial or otherwise re-contactthe server modem and establish a quick connection using the storedparameters.

FIG. 7 is a flow diagram illustrating portions of a quick reconnectprocess 700 performed by two modem devices, and FIG. 6 is a timingdiagram 600 corresponding to an illustrative quick reconnect processperformed by two modem devices. Timing diagram 600 may include acronymsand abbreviations that are often used in the context of conventionaldata communication protocols. The use of such terminology herein isintended to illustrate the concepts of the present invention in thecontext of one practical embodiment. However, the present invention maybe employed in any suitable context, and the specific signals, number ofsequences, timing of the sequences, data rates, and interaction betweenthe two modem devices shown in FIG. 6 are not intended to limit thescope of the invention in any way.

Quick reconnect process 700 may be performed by a modem system aftersuch modem system has established a communication session and,typically, after the modem system has entered a full-rate data mode. Forpurposes of this description, it may be assumed that the modem system isconfigured as described above (or is configured in an appropriate mannerto support the various process tasks described below). It may be assumedthat the two modem devices that perform process 700 are compatible withthe quick reconnect techniques described herein. Thus, process 700 neednot perform any verification or signaling to determine whether the quickreconnect procedure can be carried out.

Although not a requirement of quick reconnect process 700, the modemsystem may have been initialized in accordance with the quick startuptechniques set forth above. Accordingly, process 700 assumes that bothmodem devices have stored any number of appropriate channelcharacteristics, receiver parameters, and other information relevant tothe initialization, training, and synchronization of the modem system.As described above, such information may be suitably saved during astartup procedure or periodically during a suitable data mode. Process700 may be utilized to enable the current modem connection to be quicklyre-established following a temporary pause in the modem data mode or anyinterrupting event. In this context, a practical system can maintain acommunication link or connection between the modem devices whileallowing a user of the client modem device to temporarily pause themodem connection (or the modem data communication mode). During thetemporary holding period, the user may be able to answer anotherincoming call in response to a call waiting signal, initiate a newoutgoing call, or the like, while the client side modem device idles.

Quick reconnect process 700 may begin with a task 702, during which areconnect indication is received by the DPCM (e.g., modem 302 shown inFIG. 3). The reconnect indication may be generated in response to arequest (e.g., a user-initiated request) to terminate a temporary pausein the modem communication session. For example, a suitable reconnectsignal may be generated by the APCM (e.g., modem 304) in response to ahook flash initiated by the user of the APCM or in response to aninstruction generated by application software associated with the APCM.Alternatively, the APCM or a data access arrangement (DAA) associatedwith the APCM may generate a reconnect signal in response to a change inline current related to the on-hook status of telephone set. Suchline-in-use detection techniques are generally known to those skilled inthe art. The reconnect indication informs the DPCM that the user desiresto re-establish the current modem connection, which has been placed ontemporary hold. In a practical embodiment, the DPCM receives thereconnect indication and initiates a task 704 in response to thereconnect indication.

During task 704, the DPCM transmits a suitable reply signal thatpreferably informs the APCM that the quick reconnect procedure issupported. In the illustrative embodiment described herein, such a replysignal may include a suitable transition sequence as described above.Accordingly, quick reconnect process may perform a task 704, which maybe similar to task 414 described above in connection with FIG. 4. Forexample, task 704 may cause the DPCM to transmit the QTS signal toenable the APCM to again determine the timing phase of the DPCM (the QTSsignal is identified by reference number 602 in FIG. 6). In addition,the retransmission of the QTS signal enables the APCM to obtain RBScharacteristics of the data communication network (if necessary ordesirable to do so).

It should be noted that, for many practical modem connections, thenetwork connection (and the associated effects of digital pads and RBS)will remain consistent during the modem hold period. Of course, theremay be some situations where the network connection is cleared downduring the modem hold period to conserve network resources. In suchsituations, particularly if the same network connection is notre-established, the digital impairment profile of the network may notremain consistent. Furthermore, even if the network characteristics donot change, the APCM may lose its RBS synchronization if the modemconnection is put on hold (particularly if the APCM does not receive asignal from the DPCM during the holding period). In this respect, evenif the APCM can properly resynchronize itself to the network clock aftera holding period, the specific RBS phases may still be unknown.Accordingly, quick reconnect process 700 is preferably arranged tocontemplate that the network connection and the RBS timing has changed.

The reply signal may also include a suitable signal point sequence thatfollows the transition sequence. Accordingly, following task 704, theDPCM may perform a task 706 to suitably transmit a signal point sequenceto the APCM. As described above in connection with task 416, the signalpoint sequence may be considered to be a modified answer tone, e.g., theANSpcm signal (identified by reference number 604 in FIG. 6). The ANSpcmsignal 604 may be configured as described above, e.g., the ANSpcm signal604 may be suitably formatted to enable the APCM to determine oridentify the characteristics of the current communication channel ornetwork, particularly digital pads and/or other digital impairments. TheANSpcm signal 604 is also configured to provide a tone suitable fordisabling the network echo cancelers and disabling the network echosuppressors.

In a practical embodiment, the APCM anticipates the transmission of theANSpcm signal 604. For example, the APCM may be configured to conditionits receiver to receive the ANSpcm signal 604 after it transmits thereconnect indication to the DPCM. Accordingly, quick reconnect process700 may include a query task 708, which preferably determines whetherthe ANSpcm signal 604 has been received by the APCM and/or whether theDPCM receives a suitable acknowledgment that the APCM received theANSpcm signal 604. If not, then process 700 may exit and the modemsystem may proceed with a traditional reconnection routine. If querytask 708 determines that the ANSpcm signal 706 was properly received,then the APCM may process the received signal as described above toenable the APCM to determine the digital impairments associated with there-established channel.

A task 710 is preferably performed to cause both modem devices to recalland obtain the characteristics and parameters associated with theprevious channel connection, i.e., the channel before the modemconnection was placed on temporary hold. Task 710 may cause the DPCM toaccess previous channel information 342 and may cause the APCM to accessprevious channel information 384. As described above, this informationmay include one or more parameters related to: the current channelconditions (as previously determined), any number of settings associatedwith the modem receivers, characteristics of the communication network,or the like. Task 710 enables the modem system to quickly retrieve thesestored parameters and reset the modem devices in an appropriate mannerin lieu of an independent reassessment of the channel and in lieu of afull retraining process. Task 710 may be performed by the DPCM once itreceives the reconnect identifier from the APCM, while task 710 may beperformed by the APCM before it receives the ANSpcm signal 604. If task710 is performed by the APCM, the APCM equalizers are initializedaccording to the previous channel information 384 such that the ANSpcmsignal 604 can be properly received and analyzed.

The DPCM may reacquire its timing synchronization in accordance with anynumber of techniques, such as the conventional V.34 half-duplex primarychannel resynchronization procedure set forth in ITU-T RecommendationV.34 (International Telecommunication Union, September 1994), which isincorporated by reference herein. In other words, as shown in FIG. 6,the APCM may be configured to transmit a PP signal 610 to enable theDPCM receiver to synchronize its timing recovery and carrier recovery.The S and S\ preamble signals (reference numbers 606 and 608,respectively) may be used to initialize an automatic gain controlelement or the like. The B1 signal 612 may be considered to be apreamble sequence that may be employed to initialize the DPCM scrambler,trellis coder, and the like. These signals and sequences are set forthin detail in the V.34 Recommendation and will not be described in detailherein.

Concurrently, the DPCM may transmit an R signal 616 followed by an R\signal 618 and a B1 signal 620. These sequences also serve as suitablepreamble sequences that enable the APCM to prepare for the data mode.These signals and sequences are set forth in detail in the V.90Recommendation and will not be described in detail herein.

In response to the resynchronization sequences, the modem system entersthe data mode and the system can begin transmitting data at the fulldata rate (task 712). In other words, the data transmission mode isre-established without completely clearing down the previous connection.The data mode is identified by sequences 614 and 620 in FIG. 6. Notably,in contrast to quick startup process 400, quick reconnect process 700need not perform a comparison of the channel characteristics (see task420), an initial training procedure (see task 422), an error correctionand data compression procedure (see task 424), a final trainingprocedure (see task 428), an authentication exchange (see task 428), oran exchange of constellation and modem parameters (see task 430). Withrespect to the PAP/CHAP authentication information, the modem system maybe suitably configured to maintain the PPP/TCP/IP protocol layer duringthe hold period such that the PPP authentication data need not beretransmitted. Accordingly, the modem system may re-establish its modemconnection without wasting time performing several traditionalinitialization tasks. In a typical practical system, the quick reconnectprocess can be employed to reestablish the data mode in less than 1.5seconds.

An alternate version of the quick reconnect procedure may employ atiming diagram similar to timing diagram 500 (see FIG. 5). However, insuch an embodiment, several of the signal segments described above inconnection with timing diagram 500 can be reduced in length, thusreducing the conventional reconnect time. For example, the various TRNtraining sequences and the parameter exchange signals may be shortenedconsiderably because they need not convey essential information. Forpractical implementation reasons, it may be desirable to keep thegeneral sequence structure intact in this manner (instead of eliminatingsegments from timing diagram 500). Indeed, from a softwareimplementation standpoint, segment lengths can be adjusted in arelatively straightforward manner, while the removal of entire segmentsfrom an existing protocol may be a time consuming and arduous task.Although the reconnect time for such an alternate embodiment may belonger than that described above in connection with timing diagram 600(e.g., up to 2.5 seconds), it is still significantly less than the timerequired to perform a conventional reinitialization procedure.

As mentioned previously, call waiting and related telephony features canbe troublesome when the line is being used for a modem connection. Inresponse to a call waiting alert signal, the modem connection is oftendisrupted without the modem devices being aware of the cause of thedisruption. The call waiting alert signal may cause the modem devices todisconnect or to enter a lengthy retraining mode. Furthermore, in manyscenarios the consumer is unable to take advantage of the call waitingservice itself. Generally, the present invention addresses this problemin the following ways: (1) by allowing either modem device to request animmediate clear down in response to a call waiting alert; (2) byallowing a first modem device to request the second modem device to goon-hold, and allowing the second modem device to grant or deny therequest; and (3) by allowing either modem device to request a quickreconnect procedure (as described above). With this signaling techniquein place, the modem connection can either be cleared down, put on hold,or quickly reconnected in response to an alert signal, e.g., a callwaiting alert. Similarly, if the modem connection is put on-hold, thenthe same signaling mechanism can be employed to reconnect the modemsession after the holding period.

Assuming that both end devices (e.g., the DPCM and the APCM in a V.90system) are compatible with the modem-on-hold feature, an appropriatesignaling scheme is utilized to enable the end devices to switchoperating modes as necessary. Although the signaling scheme and variousprocesses are described herein in the context of a modem system havingan APCM at the client end and a DPCM at the server or central site end,the present invention is not so limited. For example, the techniquesdescribed herein may be equivalently applied in the context of acommunication session between two client modem devices or in the contextof a V.34 modem system.

FIG. 16 is a schematic representation of an exemplary environment inwhich a modem system 1600 may operate. Modem system 1600 generallyincludes a first modem device 1602, which may be associated with acentral site, and a second modem device 1604, which may be resident at acustomer site 1670. In the context of a typical V.90 system, first modemdevice 1602 may be the DPCM and second modem device 1604 may be theAPCM. DPCM 1602 is coupled to a central office 1606 via a digital linkand APCM 1604 is coupled to central office 1606 via an analog link,e.g., the local loop. It should be appreciated that modem system 1600may include additional elements and functionality associated with thequick startup routine and/or the quick reconnect procedure describedabove.

FIG. 16 also depicts a calling device 1608 (which is capable of placingan incoming call to the customer site), a parallel answer device 1610located at the customer site, and a series answer device 1611 located atthe customer site. As shown in FIG. 16, parallel answer device 1610 isconnected such that it receives the same calls as APCM 1604 in aconcurrent manner. In contrast, series answer device 1611 is connectedsuch that APCM 1604 routes calls to it; APCM 1604 may control orregulate the call traffic to and from series answer device 1611 in aconventional manner. A call may be established between calling device1608 and answer devices 1610 and 1611 via central office 1606, and amodem connection may be established between DPCM 1602 and APCM 1604 viacentral office 1606.

Generally, the modem system is configured to support a signalingmechanism that responds to call waiting and other situations that maycall for an interruption in the modem connection. For example, APCM 1604may transmit a suitably formatted signal to initiate a modem-on-holdstate, DPCM 1602 may transmit a different signal to acknowledge themodem-on-hold request, APCM 1604 may transmit yet another signal torequest that a quick reconnect procedure (as described above) beinitiated, and either modem device may transmit a signal that representsa clear down request. For the sake of clarity and brevity, FIG. 16depicts APCM 1604 and DPCM 1602 in a manner that relates to the exampleprocesses described herein. In practical embodiments, each of the modemdevices may be capable of functioning as a transmit or receive modem,and each of the modem devices may be capable of originating the varioussignals described herein.

DPCM 1602 includes a transmitter section 1612 and a receiver section1614, both of which may be configured in accordance with conventionaltechnologies and in accordance with the above description of modemsystem 300 (see FIG. 3). DPCM 1602 is capable of transmitting a numberof signals, sequences, and tones during initialization procedures, thedata mode, the hold mode, and transition modes. As described above, DPCM1602 may be configured to transmit a suitable transition sequence 1616and a characteristic signal point sequence (such as the ANSpcm signal1618) associated with a quick startup routine or a quick reconnectprocedure. During the data mode, DPCM 1602 transmits data 1620 inaccordance with a suitable data transmission scheme.

DPCM 1602 is also capable of transmitting a number of signals that maybe received by APCM 1604 and/or by central office 1606. For example,DPCM 1602 is capable of transmitting an “A” tone 1622 and a “B” tone1624 as described herein. In one practical embodiment, “A” tone 1622 isa 2400 Hz tone and “B” tone 1624 is a 1200 Hz tone (as set forth inITU-T Recommendation V.34). Of course, the modem devices may generateand process any suitable tones or signals in lieu of (or in addition to)these predefined tones. DPCM 1602 is also configured to transmit anumber of additional signals associated with the initiating of amodem-on-hold mode, the reconnection of a modem session after a holdingperiod, and the clearing down of a modem connection. For example, DPCM1602 may be capable of transmitting a modem hold request 1626, a modemhold acknowledgment 1628, a quick reconnect request 1630, and adisconnect signal 1632 (referred to herein as “modem status signals”).The format and function of these signals are described in more detailbelow.

DPCM 1602 may also include a signal detection element 1634, which mayemploy any number of known techniques to detect, analyze, and interpretcontrol signals, requests, and tones transmitted by APCM 1604 and/or bycentral office 1606. For example, signal detection element 1634 mayutilize a conventional tone detector and/or a conventional V.34 or V.90differential phase-shift keying (DPSK) receiver configured to detect anddistinguish the different signals described herein.

For purposes of the signaling scheme described herein, APCM 1604 ispreferably configured in a manner similar to DPCM 1602. In other words,APCM 1604 is capable of transmitting an “A” tone 1642, a “B” tone 1644,a modem hold request 1646, a modem hold acknowledgment 1648, a quickreconnect request 1650, and a disconnect signal 1652. In addition, APCM1604 may be configured to generate a caller ID tone 1654 that informscentral office 1606 that the customer site supports a caller ID feature(as depicted by the caller ID component 1656). In accordance withcurrent standards, caller ID tone 1654 is a DTMF “D” tone having alength of approximately 55-65 milliseconds. Of course, APCM 1604transmits data 1658 during the data mode.

As described above in connection with DPCM 1602, APCM 1604 preferablyincludes a signaling detection element 1660 that enables APCM 1604 toreceive, detect, and analyze the various signaling tones and sequencestransmitted by DPCM 1602. In this manner, both APCM 1604 and DPCM 1602are capable of receiving the signals and are capable of switchingoperating modes in response to the particular signal or signals that arereceived.

Central office 1606 is configured in a conventional manner to performcircuit switching associated with modem, voice, and facsimile calls.Central office 1606 may support any number of customer sites and centraloffice 1606 may be operatively coupled to any number of other centraloffices, central site modems, or the like. As described briefly above,APCM 1604, answer device 1610, and caller ID component 1656 may resideat customer site 1670. Accordingly, APCM 1604, answer device 1610, andcaller ID component 1656 are all supported by central office 1606.

Central office 1606 includes a suitable switching fabric 1672 forrouting calls between the appropriate parties. For example, switchingfabric 1672 may switch to a first state to establish a modem connectionbetween DPCM 1602 and APCM 1604 and to a second state to establish avoice connection between calling device 1608 and answer device 1610.Furthermore, switch fabric 1672 may be capable of temporarilyinterrupting a connection to impress control signals, data, or tonesonto the current circuit or line. In this respect, central office 1606may transmit a number of ring signals 1674, alert signals 1676, callerID data 1678, and other information depending upon the particularsituation. For example, in accordance with current methodologies,central office 1606 may temporarily interrupt a voice call and transmita call waiting alert signal 1676 to the customer site 1670. If thecustomer accepts the incoming call, then switch fabric 1672 may bereconfigured to route the incoming call the customer site 1670 while theoriginal call is placed on hold. As described in more detail below, asimilar routine may be employed to place modem calls on hold.

As mentioned previously, the signaling scheme preferably employs Phase 2signaling tones that are also used by conventional V.34 and V.90 modemsystems. In addition, the signaling scheme uses DPSK transmissiontechniques, which allows the signaling to integrate in a seamless mannerwith V.34 and V.90 retraining procedures. The signals are configuredsuch that they can be detected by either a V.34/V.90 DPSK receiver or bya relatively simple tone detector. In one practical embodiment, modemhold requests, modem hold acknowledgments, quick reconnect requests, anddisconnect signals are preceded by a period (e.g., at least 50milliseconds) of either tone A or tone B. This technique leverages theuse of the A and B tones, which are employed by conventional V.34 andV.90 modem systems, and takes advantage of the modulation scheme that isalready in use by the modem system. Thus, because DPCM 1602 willtypically be conditioned to receive DPSK signals, the signalingmechanism is easy to implement.

The modem status signals that follow the A or B tones are preferablytransmitted as DPSK signals based on a repeated bit pattern. In thepreferred embodiment, a modem status signal is a DPSK signal associatedwith eight repetitions of a four-bit pattern, where different patternscorrespond to different modem status signals. The use of a four-bitpattern is desirable to enable the use of a simple tone detector forsignaling detection elements 1634 and 1660; shorter bit patterns resultin a fewer number of frequency components associated with the DPSKsignal. Consequently, the signal detection scheme need not employ acomplex processing routine that analyzes a large number of frequenciesfor spectral content. Illustrative bit patterns for the different modemstatus signals are set forth in Table 3 below.

TABLE 3 Modem Status Signals Modem Status Signal Signal AbbreviationDPSK Pattern Disconnect Signal DC 0101 Modem Hold MH 0011 Request ModemHold MHA 0001 Acknowledge Quick Reconnect QRR 0111 Request

The particular bit patterns are preferably selected such that theresultant DPSK signal is distinguishable over DPSK signals that are“reserved” for use in the context of other data communication protocols.For example, a DPSK pattern of all zeros is equivalent to the A or Btones, and a DPSK pattern of all ones is equivalent to the V.34 INFOMARKsignal. In addition, the particular bit patterns may be suitablyselected such that the resultant DPSK signal is easy to detect by a tonedetector. For the example bit patterns set forth in Table 3, the modemstatus signals will have the frequency content listed in Tables 4 and 5below, where the frequencies are in Hertz, an “X” indicates spectralcontent greater than a threshold level, and a slash indicates spectralcontent that is lower than the threshold level. For the example DPSK bitpatterns shown in Table 3, a lower spectral energy component is at least8 dB down from a higher spectral energy component at the same frequency.Consequently, the different modem status signals can be distinguishednotwithstanding the existence of some shared frequency components.

TABLE 4 Frequency Components for Modem Status Signals (APCM) 900 9751050 1125 1200 1275 1350 1425 1500 DC X X MH X X X X X MHA — X X — QRR X— — X

TABLE 5 Frequency Components for Modem Status Signals (DPCM) 2100 21752250 2325 2400 2475 2550 2625 2700 DC X X MH X X X X X MHA — X X — QRR X— — X

The different frequency ranges employed by the APCM and DPCM are relatedto an exemplary application where different carriers are used by the twomodem devices. For example, in a conventional V.90 system, the DPCM usessignaling near 2400 Hz (tone “B” and the DPSK carrier), while the APCMuses signaling near 1200 Hz. This feature was derived from theconventional V.34 scheme where the calling modem uses signaling near1200 Hz and the answer modem uses signaling near 2400 Hz. Consequently,the two spectral patterns are the same but for the shift between 1200 Hzand 2400 Hz. This methodology ensures that the end devices can properlydetect the signals even where both ends are transmitting the same typeof signal.

In a practical system, the modem status signal detection need not detectthe entire “spectral fingerprint” for the given signals. Rather, signaldetection elements 1634 and 1660 may be configured to detect and analyzea distinctive number of the spectral components for purposes ofindicating a match. For example, as shown in Table 4, if a signalcontains relatively high spectral energy at 1050 Hz and 1350 Hz, thenthe signal may be a disconnect signal or a modem hold request.Accordingly, the signal detection routine will continue to analyze thesignal for spectral content at 900 Hz, 1200 Hz, and/or 1500 Hz and makethe appropriate decision.

FIG. 8 is a timing diagram that depicts the situation where a currentmodem connection is interrupted by a call waiting indication and themodem connection is placed on hold while the incoming call is answeredby the client end. FIG. 8 is applicable regardless of whether customersite 1670 employs parallel answer device 1610 or series answer device1611. The progression of signals, sequences, tones, commands, and thelike are shown with respect to an APCM, a DPCM, and a central office(the central office may be associated with signals to the APCM andsignals to the DPCM). For convenience, the process associated with FIG.8 is described herein in the context of modem system 1600.

During the data mode, central office 1606 temporarily interrupts themodem connection and sends an alert signal 802 to APCM 1604. The alertsignal may be a conventional call waiting alert and it may include acomponent that is audible to humans (e.g., an audio tone) and acomponent that is detectable by data communication devices or machines.In accordance with most call waiting protocols, the alert signalcomponents are transmitted in series. In response to alert signal 802,APCM 1604 may send a DTMF tone 804 to request caller ID information fromcentral office 1606. As described above, tone 804 may be a short burstof a DTMF “D” tone having a duration of about 55-65 milliseconds.Assuming that central office 1606 receives and recognizes DTMF tone 804,it will format and transmit the caller ID data 805 back to the customersite 1670. As shown in FIG. 16, the caller ID data 805 (represented byreference number 1678 in FIG. 16) may be received and processed in asuitable manner for display or analysis by caller ID component 1656.

In response to the switching out of APCM 1604 by central office 1606,DPCM 1602 begins a retrain procedure by transmitting an appropriatesignal, e.g., a “B” tone 806. In a practical application, the “B” tone806 is usually transmitted while the caller ID request 804 and caller IDdata 805 is being received, processed, and transmitted by central office1606. The “B” tone 806 is continuously transmitted while DPCM 1602 waitsfor APCM 1604 to reply with an “A” tone 808. APCM 1604 may transmit the“A” tone 808 if it receives the “B” tone 806 from DPCM 1604. Asmentioned above, the “A” tone 808 is preferably transmitted for at leasta minimum duration, e.g., 50 milliseconds, to give DPCM 1602 theopportunity to receive it. If DPCM 1602 does not receive an “A” tone 808within a specific time period, then it may eventually disconnect itself.

Assuming that the user of APCM 1604 desires to answer the incoming call,then a modem hold request 810 is transmitted following the “A” tone 808.Modem hold request 810 may be prompted automatically by a suitabledevice resident at the customer site 1670 or it may be prompted inresponse to a user command. Modem hold request 810, which may beformatted as described above, is preferably transmitted for at least aminimum period of time. In one practical embodiments modem hold request810 is transmitted for approximately 53 milliseconds (all of the modemstatus signals described herein may have a similar minimum duration). Incontrast to a conventional V.34 or V.90 modem system, an actualretraining procedure is not performed upon receipt of the “A” tone 808by DPCM 1602. Rather, in response to modem hold request 810, DPCM 1602may transmit a modem hold acknowledgment 812 for a minimum period oftime, e.g., approximately 53 milliseconds.

After DPCM 1602 transmits modem hold acknowledgment 812, it preferablycontinues to transmit the “B” tone 806 while it maintains a hold state.In response to modem hold acknowledgment 812, APCM 1604 may generate asuitable flash signal 814 to instruct central office 1606 to switch outthe modem connection and to switch in the incoming call 816. Inaddition, the handset (or other suitable answer device) begins toreceive the incoming call; APCM 1604 may be configured to route theincoming signal to parallel answer device 1610 or serial answer device1611 in an appropriate manner. In addition, APCM 1604 may be placed inan idle or “on-hook” state while the handset is connected (during period818). Accordingly, the user at customer site 1670 may proceed with theincoming call 816 while DPCM 1602 remains on hold. The modem connectionmay be re-established by way of a quick modem reconnect procedure(described below).

FIG. 9 is a timing diagram that depicts a situation where DPCM 1602 isto be reconnected in response to the termination of the incoming call.The process shown in FIG. 9 assumes that: (1) DPCM 1602 is in a holdstate; (2) answer device 1610 is connected in parallel with APCM 1604;and (3) answer device 1610 terminates the incoming call, e.g., answerdevice 1610 is placed “on-hook” before calling device 1608 is placed“on-hook”. For purposes of this description, the parallel connectionmeans that APCM 1604 and answer device 1610 receive the same signalsfrom central office 1606 in a concurrent manner.

In response to the termination of the incoming call, central office 1606will detect the “hang up” in a conventional manner, e.g., using wellknown line detection techniques. Eventually, central office 1606switches out or disconnects the incoming call, switches in DPCM 1602,and generates a suitable signal, e.g., a ring signal 902. Ring signal902 serves to alert the user at customer site 1670 that the originalcall is still holding and is ready to be reconnected. In response toring signal 902, APCM 1604 is placed “off-hook” such that it can againreceive signals from central office 1606. Thus, ring signal 902 mayinform APCM 1604 that the incoming call has been cleared and/or thatAPCM 1604 may proceed with a modem reconnect procedure. As describedabove in connection with FIG. 8, APCM 1604 generates an “A” tone 904(for at least 50 milliseconds) in response to the detection of a “B”tone 906. Following the “A” tone 904, APCM 1604 may transmit a quickreconnect request 908 to initiate a quick reconnect procedure (asdescribed above in the context of FIGS. 6 and 7. Accordingly, inresponse to the detection of quick reconnect request 908, DPCM 1602preferably transmits a QTS signal 910 followed by an ANSpcm sequence912. The characteristics, format, and function of QTS signal 910 andANSpcm sequence 912 are as described above. Assuming that both modemdevices support the quick reconnect feature described above, the heldmodem connection may be re-established in a relatively short period oftime.

FIG. 10 is a timing diagram that depicts the situation where theincoming call is terminated before parallel answer device 1610 is placed“on-hook”. In this scenario, when the termination of the incoming callis initiated by the calling device 1608, central office 1606 willreconnect the customer site 1670 to the original call (which is a modemconnection in this example). Consequently, the “B” tone transmitted byDPCM 1602 will again be made available at APCM 1604. Regardless ofwhether APCM 1604 is currently in an “on-hook” or an “off-hook” state,it preferably detects that DPCM 1602 has been reconnected. It should beappreciated that APCM 1604 may employ any number of known techniques(which can vary depending upon the specific implementation) to detectthe reconnection. For example, DPCM 1602 may detect the “B” tone fromDPCM 1602, it may automatically react after a predetermined timeoutperiod, or it may utilize line-in-use techniques to sense thetermination of the incoming call. Once the two modem devices haveresumed communicating with one another, the quick reconnect routineproceeds as described above in connection with FIG. 9.

With respect to the situation depicted in FIG. 10, it may be necessaryto have APCM 1604 respond within certain time periods to ensure thatcentral office 1606 does not consider the reconnect attempt to be a hookflash or a disconnect. For example, in a preferred embodiment, APCM 1604is configured to respond to the termination of the incoming call within200 milliseconds such that central office 1606 does not interpret thedelay as a conference call request (which may cause DPCM 1602 to beplaced on hold) or a disconnection (which may cause a clear down of theconnection). The particular time periods may be selected in accordancewith any suitable telecommunication recommendation, standard, oroperating protocol, such as the BELLCORE Technical Reference GR-506-CORE(related to general telecommunication signaling) and the BELLCORETechnical Reference TR-NWT-000575. The contents of these references isincorporated by reference herein.

In general, any of the procedures utilized in the context of a systemusing parallel answer device 1610 may also be used in the context of asystem using series answer device 1611. However, the converse may notalways be true. For example, FIG. 11 is a timing diagram that depictsthe situation where the incoming call is terminated by series answerdevice 1611. As described above, a communication line at customer site1670 initially provides APCM 1604 with a signal from central office1606, and APCM 1604 routes the signal to answer device 1610. In mostpractical applications, APCM 1604 will remain “off-hook” even if it ismerely routing the call to series answer device 1611. Accordingly, APCM1604 is capable of monitoring the line for the presence of a “B” tone ora suitable signal associated with DPCM 1602. In this scenario, if theincoming call is terminated (by calling device 1608 or by series answerdevice 1611), APCM 1604 is capable of receiving signals from centraloffice 1606 Furthermore, central office 1606 responds to the detectionof the call termination by switching DPCM 1602 to communicate with thecustomer site 1670. Thus, if the “B” tone is detected by APCM 1604, itcan immediately decouple the series answer device 1611. Once the twomodem devices resume the communication session, the quick reconnectroutine proceeds as described above in connection with FIG. 9.

FIG. 12 is a timing diagram that depicts the situation where DPCM 1602responds to a modem hold request with a clear down instruction (FIG. 12is applicable to a system that uses either serial answer device 1611 orparallel answer device 1610). Up to the point where a modem hold request1202 is transmitted from APCM 1604 to DPCM 1602, the process is similarto that described above in connection with FIG. 8. In contrast to thescenario where DPCM 1602 acknowledges modem hold request 1202, thesituation depicted in FIG. 12 calls for the transmission of a disconnectsignal 1204 from DPCM 1602. DPCM 1602 may transmit disconnect signal1204 after contemplating or considering any number of operatingparameters, e.g., the current call traffic, the functional capabilitiesof DPCM 1602, the channel characteristics, or the like.

After DPCM 1602 transmits disconnect signal 1204, it idles or waitswithout transmitting any meaningful signals. In response to disconnectsignal 1204, APCM 1604 clears down the modem connection in anappropriate manner. If central office 1606 does not detect activity fromAPCM 1604 after a suitable timeout period, e.g., 1550 milliseconds, thenit may assume that APCM 1604 has been disconnected. Thereafter, centraloffice 1606 switches out DPCM 1602 and generates ring signals 1206 andcaller ID data 1208 to customer site 1670 such that the incoming callcan be answered. DPCM 1602 may clear down its modem connection after asuitable timeout period, e.g., two seconds, during which it receives nosignals from APCM 1604. Accordingly, DPCM 1604 will typically hang uponce central office 1606 begins generating ring signal 1206. Asdescribed above, prior to clear down, APCM 1604 and/or DPCM 1602 maysave any number of relevant operational parameters to facilitate a quickstartup for subsequent connections.

Under certain conditions, the end user may wish to immediately terminatethe modem connection and accept an incoming call. FIG. 13 is a timingdiagram that depicts a situation where, in response to an alert signal1302, APCM 1604 transmits a disconnect signal 1304 rather than a modemhold request. FIG. 13 is applicable to a system that uses either serialanswer device 1611 or parallel answer device 1610. APCM 1604 maygenerate disconnect signal 1304 in response to a user command orautomatically in accordance with a predetermined protocol or setting.The progression of signals and operations associated with FIG. 13 issubstantially similar to the progression associated with FIG. 12.However, unlike the process depicted in FIG. 12, APCM 1604 transmitsdisconnect signal 1304 to DPCM 1602.

FIG. 14 is a timing diagram that depicts the scenario where, in responseto an alert signal 1401, APCM 1604 prompts a quick reconnect procedureand ignores the incoming call. FIG. 14 is applicable to a system thatuses either serial answer device 1611 or parallel answer device 1610.Such a situation may occur when the quality of the modem connection isimportant, when the end user does not want to be disturbed by incomingcalls, and/or if the modem connection is severely affected by the alertsignal 1401. Furthermore, such a situation may occur in response to thecaller ID data, i.e., the answering party may choose to ignore incomingcalls from certain calling parties. Up to the point where an “A” tone1402 is transmitted, the procedure of FIG. 14 is similar to theprocedure of FIG. 8. Following the transmission of “A” tone 1402, APCM1604 generates a quick reconnect request 1404, which is eventuallyreceived by DPCM 1602. In response to quick reconnect request 1404, DPCM1602 may transmit a QTS signal 1406 followed by an ANSpcm signal 1408 tofacilitate the quick reconnect routine (as described above in connectionwith FIGS. 6 and 7). It should be noted that APCM 1604 may alternativelytransmit a suitable modem status signal, e.g., a phase reversal, thatindicates a full retrain procedure rather than a quick reconnectprocedure. In such an embodiment, the retrain procedure would proceed ina conventional manner.

Under some conditions, DPCM 1602 may not “automatically” enter theinitial retrain mode in response to an alert signal. In other words,DPCM 1602 may continue transmitting data as though no interruption hasoccurred. FIG. 15 is a timing diagram that illustrates this situation(FIG. 15 is applicable to a system that uses either serial answer device1611 or parallel answer device 1610). As described above in connectionwith FIG. 8, APCM 1604 may respond to an alert signal 1502 bytransmitting a DTMF “D” tone 1504 (associated with a caller ID request)during an interruption in the data mode. Unlike the situation of FIG. 8,where DPCM 1602 begins to transmit a “B” tone as a result of theinterruption, DPCM 1602 continues to transmit data 1506 to APCM 1604.When APCM 1604 is reconnected by central office 1606, it preferablytransmits an “A” tone 1508 for a suitable time period to allow DPCM 1602to respond with a “B” tone 1510. When APCM 1604 detects the “B” tone1510 from DPCM 1602, it then follows the “A” tone 1508 with a SIGNAL_(A)1512, where SIGNAL_(A) 1512 may be a modem hold request, a quickreconnect request, or a disconnect signal. In response to SIGNAL_(A)1512, DPCM 1602 transmits a SIGNAL_(D) 1514, where SIGNALD may be amodem hold acknowledgment, a short period of silence followed by a QTSsignal and an ANSpcm sequence, or a disconnect signal. In this manner,the different situations described above can be handled even though DPCM1602 does not initially enter the retrain mode with the transmission ofa “B” tone.

The signaling routines and procedures described above in connection withFIGS. 8-16 can be equivalently applied to accommodate various requeststhat originate at customer site 1670. For example, the user of APCM 1604may desire to place a current modem connection on hold, to prompt aquick reconnect, or to prompt a full retrain in an independent manner.In one practical embodiment, the modem hold request and modem holdacknowledgment signals can be incorporated into the conventional Phase 4CP and MP sequences. Accordingly, if either modem device wants to placethe other modem device on hold (e.g., for three-way calling), then therequesting modem device can perform a rate renegotiation and transmitthe hold signal in an appropriate manner. This technique may beperformed in a similar manner as the conventional V.34 and V.90 cleardown procedure, where a special code (data rate=0) is used to indicate aclear down. However, the modem hold signaling technique may utilize adifferent bit combination or leverage a number of reserved bits.

In response to such a user request, APCM 1604 may generate an “A” tonefollowed by an appropriate modem status signal (e.g., a modem holdrequest, a quick reconnect request, or the like) for receipt by DPCM1602. As described above in connection with FIG. 15, DPCM 1602 may thenrespond with a “B” tone followed by an appropriate status signal reply(e.g., a modem hold acknowledgment, a QTS signal, or the like). In thismanner, the techniques of the present invention can be applied in anynumber of situations unrelated to a call waiting alert, a lineinterruption, or a line corrupting event.

In one embodiment, the present invention provides techniques to reducethe initialization period and reconnect period normally associated witha V.90 modem system. The quick startup and quick reconnect techniquesleverage the known channel characteristics of a previous connection toreduce the training time associated with subsequent attempts toestablish the same connection. Although not limited to any specificmodem application, the quick startup procedure may be used to eliminateportions of the initialization protocols or processes normally employedby a 56 kbps modem, e.g., V.8bis, V.8, digital impairment learning,initial training, probing and ranging, or the like. In addition, thequick startup technique may perform certain operations at a differenttime or in a different order in comparison to a conventional modemstartup technique.

Referring back to FIG. 5, it is shown that during the phase 4 of theV.90 training process the APCM modem 590 and the DPCM modems 580exchange various parameters via CP and MP frames 510 and 520,respectively. FIG. 17 shows various bits of information and parametersthat may be included in an example MP sequence or frame 1700.

Referring to FIG. 17, it is seen that the MP frame 1700 has asynchronous format and includes seventeen sync bits 1701 of “1”s (bits0:16), followed by one start bit 1702 (bit 17) and ending with sixteenbits of CRC 1730 (bits 171:186). The CRC bits 1730 are utilized by theAPCM modem 580 to verify the sanctity of the MP frame 1700. As shown,the MP frame 1700 also includes a reserved bit 1704 (bit 19) that isavailable for future use. The MP frame 1700 further includes anacknowledgement bit 1710 (bit 33). The acknowledgement bit 1710 is “0”.Other bits of information in the MP frame 1700 include data signalingrates, trellis encoder select bit, nonlinear encoder parameter selectbit, constellation select bit, data signaling rate capability mask,asymmetric data signaling rate enable and many bits of precedinginformation.

The acknowledgement bit 1710 is set to a “1” by the DPCM modem 590 toacknowledge the receipt of the CP frame 510 (see FIG. 5) transmitted bythe APCM modem 580. The MP frame 1700 with the acknowledgement bit 1710set to a “1” is denoted as the MP′ frame 522 (see FIG. 5). It should benoted that both the MP frame 510 and the MP′ frame 512 include the samenumber of bits and information with a single difference being the valueof the acknowledge bit 1710.

With reference to FIG. 18, an example definition bits of a CP frame 1800is shown. Similar to the MP frame 1700, the CP frame 1800 is asynchronous type frame with seventeen synchronous leading bits 1801 of“1”s (bits 0:16), followed by one start bit 1802 (bit 17) and endingwith sixteen bits of CRC 1830 (bits 273+δ:288+δ). The CRC bits 1830 areutilized by the DPCM modem 590 to verify the sanctity of the CP frame1800. As shown, the CP frame 1800 also includes a reserved bit 1804 (bit18) that is available for future use. The CP frame 1800 further includesan acknowledgement bit 1810 (bit 33). The acknowledgement bit 1810 is“0”. Other bits of information in the CP frame 1800 include datasignaling rates, silent period bit, sign bits for spectral shapingparameters, constellation information and many other bits of informationincluding variable length parameters that can lengthen the size of theCP frame 1800 even more.

The acknowledgement bit 1810 is set to a “1” by the APCM modem 580 toacknowledge the receipt of the MP frame 520 (see FIG. 5) transmitted bythe DPCM modem 590. The CP frame 1800 with the acknowledgement bit 1810set to a “1” is denoted as the CP′ frame 522 (see FIG. 5). Both the CPframe 510 and the CP′ frame 512 include the same number of bits andinformation with a single difference being the value of the acknowledgebit 1810.

Referring to FIG. 19, preliminary definition bits of a CPa frame 1900for possible inclusion in the ITU V.92 Recommendation is shown. Similarto the MP and CP frames 1700 and 1800, the CPa frame 1900 is asynchronous type frame with seventeen synchronous leading bits 1901 of“1”s (bits 0:16), followed by one start bit 1902 (bit 17) and endingwith sixteen bits of CRC 1930. The CRC bits 1930 are utilized by theAPCM modem (see FIG. 24 c) to verify the sanctity of the CPa frame 1900.As shown, the CPa frame 1900 also includes reserved bits 1904 (bits21:23) that are yet to be defined. The CPa frame 1900 further includesan acknowledgement bit 1910 (bit 33). The acknowledgement bit 1910 forthe CPa frame 1900 is “0”. The acknowledgement bit 1910 is set to a “1”by the DPCM modem to acknowledge the receipt of the CP frame (see FIG.24 c) transmitted by the APCM modem. Other bits of information in theCPa frame 1900 include constellation information with high resolution aswell as precoder and prefilter coefficients and many other bits ofinformation including variable length parameters that can significantlyincrease the length of the CPs frame 1900.

If the acknowledgement mechanisms of the ITU Recommendations V.34 andV.90, as explained with reference to FIGS. 17 and 18, were to be usedfor the ITU Recommendation V.92, the CPa frame and the CPa′ frame wouldinclude the same number of bits and information with a single differencebeing the value of the acknowledge bit 1910.

The parameter exchange and acknowledgement mechanisms used in the V.34and V.90 Recommendations, however, have introduced a significantoverhead and delay in the training process. As shown in FIG. 5, themodems 580 and 590 transmit CP and MP frames 510 and 520 continuouslyuntil an acknowledgement frame from the remote modem is received. Eventhe acknowledgement frames introduce a significant overhead and delay inthe handshaking process, because the same previously transmittedinformation bits are unnecessarily retransmitted over and over again.These continuous transmissions and retransmissions of CP, MP, CP′ andMP′ frames are needless, since in most cases, the first transmission ofthe MP or CP frame is received correctly by the remote modem.Accordingly, it becomes unnecessary to retransmit all the informationbits in the MP′ or CP′ frame, since the acknowledgement bit is in factthe most significant bit of information.

To eliminate this enormous overhead and delay during the handshakingprocess, the present invention introduces short parameter frames, asshown in embodiments of FIGS. 20-22. Referring to FIG. 20, an exampledefinition bits of a short NP frame (NPs) 2000 is shown. As shown, justlike the MP frame 1700, the MPs frame 2000 is a synchronous type framewith seventeen synchronous leading bits 2001 of “1”s (bits 0:16),followed by one start bit 2002 (bit 17) and ending with sixteen bits ofCRC 2030 (bits 35:50). The CRC bits 2030 are utilized by the APCM modem580 to verify the sanctity of the MPs frame 2000. As further shown, theMPs frame 2000 also includes an MPs indicator bit 2004 (bit 19) todistinguish the MPs frame 2000 from the MP frame 1700. Referring back toFIG. 17, it is noted that the corresponding bit location is the reservedbit 1704. The MPs frame 2000 further includes an acknowledgement bit2010 (bit 33). The acknowledgement bit 2010 is “0”. The acknowledgementbit 2010 is set to “1” by the DPCM modem to acknowledge the receipt ofthe CP frame (see FIG. 24 b) transmitted by the APCM modem. The MPsframe 2000 with the acknowledgement 2010 set to a “1” is denoted as theMPs′ frame. Both the MPs frame and the MPs′ frame include the samenumber of bits and information with a single difference being the valueof the acknowledge bit 2010. However, the MPs and MPs′ frames aresubstantially shorter than the MP and MP′ frames, respectively.

Now, referring to FIG. 21, an example definition bits of a short CPframe (CPs) 2100 is shown. As shown, just like the CP frame 1800, theCPs frame 2100 is a synchronous type frame with seventeen synchronousleading bits 2101 of “1”s (bits 0:16), followed by one start bit 2102(bit 17) and ending with sixteen bits of CRC 2130 (bits 35:50). The CRCbits 2130 are utilized by the DPCM modem 590 to verify the sanctity ofthe CPs frame 2100. As further shown, the CPs frame 2100 also includes aCPs indicator bit 2104 (bit 18) to distinguish the CPs frame 2100 fromthe CP frame 1800. Referring back to FIG. 18, it is noted that thecorresponding bit location is the reserved bit 1804. The CPs frame 2100further includes an acknowledgement bit 2110 (bit 33). Theacknowledgement bit 2110 is “0”. The acknowledgement bit 2110 is set to“1” by the APCM modem to acknowledge the receipt of the MP frame (seeFIG. 24 b) transmitted by the DPCM modem. The CPs frame 2100 with theacknowledgement 2110 set to a “1” is denoted as the CPs′ frame. Both theCPs frame and the CPs′ frame include the same number of bits andinformation with a single difference being the value of the acknowledgebit 2110. It should be noted, however, that the CPs and CPs′ frames aresubstantially shorter than the CP and CP′ frames, respectively.

With reference to FIG. 21, an example definition bits of a short CPaframe (CPas) 2200 is shown. As shown, just like the CPa frame 1900, theCPas frame 2200 is a synchronous type frame with seventeen synchronousleading bits 2201 of “1”s (bits 0:16), followed by one start bit 2202(bit 17) and ending with sixteen bits of CRC 2230 (bits 35:50). The CRCbits 2230 are utilized by the APCM modem to verify the sanctity of theCPas frame 2200. As further shown, the CPas frame 2200 also includesCPas indicator bits 2104 (bits 18:20) to distinguish the CPas frame 2200from the CPa frame 1900. Referring back to FIG. 19, it is noted that thecorresponding bits are the reserved bits 1904. The CPas frame 2200further includes an acknowledgement bit 2210 (bit 33). Theacknowledgement bit 2210 is “0”. The acknowledgement bit 2210 is set to“1” by the DPCM modem to acknowledge the receipt of the CP frame (seeFIG. 24 c) transmitted by the APCM modem. The CPas frame 2200 with theacknowledgement 2210 set to a “1” is denoted as the CPas′ frame. Boththe CPas frame and the CPas′ frame include the same number of bits andinformation with a single difference being the value of the acknowledgebit 2210. It is also that the CPas and CPas′ frames are substantiallyshorter than the CPa and CPa′ frames, respectively.

FIG. 23 illustrates a conventional exchange of parameters embedded in MPsequences or frames 2312 and 2322 between an APCM modem 2310 and a DPCMmodem 2320, respectively, in accordance with the ITU RecommendationV.34. As shown, after the TRN portions 2311 and 2312 of the phase 4 orthe final training of the handshaking process, the APCM and DPCM modems2310 and 2320 exchange the MP frames 2312 and 2322, respectively. The MPframes 2312 and 2322 are in the form shown in the MP frame 1700 of FIG.17. As shown, the DPCM modem 2320 starts transmitting the MP frame 2322shortly before the APCM starts its transmission of the MP frame 2312. Asa result, the APCM modem 2310 receives the MP frame 2322 prior to theDPCM modem 2320 receiving the MP frame 2312. In response, the APCM modem2310 sets the acknowledgement bit in the MP frame, thus creating an MP′frame, and starts transmitting the MP′ frame 2314, including each andevery bit of information previously transmitted to the DPCM modem 2320via the MP frame 2312. While the DPCM is awaiting an acknowledgement forits MP frame 2322 from the APCM modem 2310, another MP frame 2322 istransmitted by the DPCM modem 2320 to the APCM modem 2310 to provide theAPCM modem 2310 with a second chance to receive the MP frame 2322. Inthe mean time, the APCM modem 2310 has already received the first MPframe 2322 and no acknowledgement for its MP frame 2312 or its MP′ frame2314, accordingly, the APCM modem 2310 generates a second MP′ frame togive the DPCM a third chance to receive the parameters embedded in theMP or MP′ frame 2312 or 2314, respectively. As shown, however, the DPCMmodem 2320 had already started transmitting an MP′ frame 2324. Theselong frames and their overlap in the transmission and reception timedomains prevent the modems 2310 and 2320 to quickly exchange parameters.The delay is in fact cumulative. The transmission and reception of thelong MP and MP′ frames cause one modem to start transmitting a long MPframe while receiving an MP′ frame from the remote modem; however, theMP′ frame may not be sanctified until the CRC bits are received andverified. Therefore, the modem receiving the MP′ frame startstransmitting another long MP frame needlessly.

Referring back to FIG. 5, it is also noted that long CP, CP′, MP andMP′frames 510, 512, 520 and 522, respectively, are exchanged many times,not because of errors in transmission, but merely because of timingdifferences in transmission and reception of these frames. It is indeedclear that utilizing a similar mechanism for the ITU Recommendation V.92will lead to even longer delays due to the fact that the CPa frames areconsiderably longer than the MP and CP frames.

Accordingly, in one embodiment of the present invention, as shown inFIG. 24 a, short MP and MP′ frames (MPs and MPs′) 2423 and 2424,respectively, similar to the MPs frame 2000 in FIG. 20, are utilized tosubstantially reduce the parameter exchange time and obtain a quickerconnection between the modems. Referring to FIG. 24 a, just as in FIG.23, the two modems 2410 and 2420 exchange long MP frames 2412 and 2422,respectively. However, after such transmissions, both modems switch toshort MP frame formats. As shown, the DPCM modem 2420 startstransmitting the MPs frames 2423 immediately after transmitting the MPframe 2422 and while waiting to receive the entire MP frame 2412 fromthe APCM modem 2410. Immediately after transmitting the MP frame 2412,the APCM modem 2410 acknowledges the receipt of the MP frame 2422 fromthe DPCM modem 2420 by sending a short MP′ frame 2414 (MPs′). On theother hand, while sending the MPs frames 2423, the DPCM modem 2420receives the MP frame 2412 and acknowledges that frame by sending anMPs′ frame 2424. The transmission of the short frames causes asubstantial reduction in the handshaking time and results in a quickconnection between the two modems 2410 and 2420.

By the same token, the exchange of short CP and MP frames in FIG. 24 bwill speed up the connection time for the V.90 compliant modems. Asshown, short MP, MP′, CP and CP′ frames (MPs, MPs′, CPs and CPs′) 2463,2464, (not shown) and 2454, respectively, similar to the MPs frame 2000in FIG. 20 and the CPs frame 2100 in FIG. 21, respectively, may beutilized for the V.90 compliant modems. The use of these short framessubstantially reduces the parameter exchange time and causes a quickerconnection between the modems. Referring to FIG. 24 b, the two modems2450 and 2460 exchange long CP and MP frames 2452 and 2462,respectively. After the transmission of these long frames, the modemsstart transmitting the short CP and MP frame types. As shown, the DPCMmodem 2460 starts transmitting the MPs frames 2463 immediately aftertransmitting the MP frame 2462 and while waiting to receive the entireCP frame 2452 from the APCM modem 2450. Immediately after transmittingthe CP frame 2452, the APCM modem 2450 acknowledges the receipt of theMP frame 2462 from the DPCM modem 2460 by sending a short CP′ frame 2454(CPs′). At the other end, while sending the MPs frames 2463, the DPCMmodem 2460 receives the CP frame 2452 and acknowledges that frame bysending an MPs′ frame 2464.

The transmission of short frames will result in a quick connection, inparticular for the V.92 compliant modems, mainly because of the volumeof the information and parameters embedded in the CPa frames 1900 (seeFIG. 19). Referring to FIG. 24 c, short CPa, CPas′, CP and CP′ frames(CPas, CPas′, CPs and CPs′) 2493, 2494, (not shown) and 2484,respectively, similar to the CPas frame 2200 in FIG. 22 and the CPsframe 2100 in FIG. 21, respectively, may be utilized for the V.92compliant modems. The use of these short frames substantially reducesthe parameter exchange time. As a result, the V.92 compatible modems canachieve a quick connection. Referring to FIG. 24 c, the two modems 2480and 2490 first exchange long CP and CPa frames 2482 and 2492,respectively. After the transmission of these long frames, the modemsstart transmitting the short CP and CPa frame types. As shown, the DPCMmodem 2490 starts transmitting the CPas frames 2493 immediately aftertransmitting the CPa frame 2492 and while waiting to receive the entireCP frame 2482 from the APCM modem 2480. Immediately after transmittingthe CP frame 2482, the APCM modem 2480 acknowledges the receipt of theCPa frame 2492 from the DPCM modem 2490 by sending a short CP′ frame2484 (CPs′). At the other end, while sending the CPas frames 2493, theDPCM modem 2490 receives the CP frame 2482 and acknowledges that frameby sending a CPas′ frame 2494.

FIGS. 25 a, 25 b and 25 c illustrate a few examples of situations wherethe long frames, MP, CP and/or CPa are not received properly by areceiving modem. Referring to FIG. 25 a, according to one embodiment ofthe present invention, the APCM and DPCM modems 2510 and 2520 exchangeMP frames 2512 and 2522, respectively. Immediately after thetransmission of the long MP frames 2512 and 2522, both modems 2510 and2520 switch to transmissions of short MP frames 2513 and 2523,respectively. As shown, the DPCM modem 2520 receives the MP frame 2512properly. Accordingly, in response, the DPCM modem 2520 acknowledges theMP frame 2512 with an MPs′ frame 2524. At the other end, however, theAPCM 2510 fails to receive the MP frame 2522. This failure may resultfrom various reasons, such as a bad transmission, bad line conditions,wrong CRC, etc. As a result of this failure, the APCM modem 2510continues transmitting MPs frames 2513 with the acknowledgement set to“0” indicating that the MP frame 2522 has not been received. In suchsituations, according to one embodiment of the present invention, theDPCM modem 2520 starts transmitting the long MP frames once again.Because the DPCM modem 2520 has already received the MP frame 2512, thenew long MP frames 2525 transmitted by the DPCM modem 2520 will havetheir acknowledgement bits set to “1”. In other words, the DPCM modem2520 starts transmitting MP′ frames, since the short frames do notinclude all the required parameters. In some embodiments, the DPCM modem2520 may send only one MP′ frame 2525 and then switch to sending MPs′frames 2524 (e.g., FIG. 25 b).

The DPCM modem 2520 may use various conditions, events or methods indetermining when to start retransmitting long MP frames after a periodof transmitting short MP frames. In one embodiment, if the DPCM modem2520 or the APCM modem 2510 receives the beginning of an MP or MPs framemore than a round-trip delay after the modem 2520 or 2510 has completedits own transmission of a long MP frame, then the modem 2520 or 2510 maystart transmitting long MP frames once again. In another embodiment,extra time, for example 20-30 ms, may be added to the round-trip delaytime to allow for detection delay, before long MP frames are transmittedonce again. Those of ordinary in the art are familiar with thecalculation of round-trip delays. In some embodiments, a fixed amount oftime may be used as a time-out period in determining when the modemshould send a long MP frame once again after sending short MP frames. Inyet another embodiment, a predetermined event may be utilized, such asthe number of short MP frames transmitted by the modem that is awaitingan acknowledgement. For example, if the APCM modem 2510 transmits threeMPs frames, but does not receive an acknowledgement, then the APCM modem2510 may transmit another MP frame.

Now, referring to FIG. 25 b, according to another embodiment of thepresent invention, the APCM and DPCM modems 2550 and 2560 exchange CPand MP frames 2552 and 2562, respectively. Immediately after thetransmission of the long CP and MP frames 2552 and 2562, both modems2550 and 2560 switch to transmissions of short CP (CPs) and short MP(MPs) frames 2553 and 2563, respectively. As shown, the DPCM modem 2560receives the CP frame 2552 properly. Accordingly, in response, the DPCMmodem 2560 acknowledges the CP frame 2552 with an MPs′ frame 2564. Atthe other end, however, the APCM 2550 fails to receive the MP frame2562. Therefore, the APCM modem 2550 continues transmitting CPs frames2553 with the acknowledgement set to “0” indicating that the MP frame2562 has not been received. As shown, the DPCM modem 2560 stopstransmitting MPs′ frames 2564 and transmits only one long MP, having theacknowledgement bit set (because CP has been received), i.e., MP′. Insome embodiments, the DPCM modem 2560, may continue sending more MP′frames. In the embodiment of FIG. 25 b, however, the DPCM modem 2560starts sending MPs′ frames 2564 after sending only one MP′ frame. In themean time, the APCM modem 2550 continues sending short CP frames 2553,since it has received the MPs′ frame 2564 as acknowledgement.Eventually, the APCM modem 2550 receives the long MP frame 2565 from theDPCM modem 2560 and the modems move to the data phase. As stated withreference to FIG. 25 a, various methods or predetermined conditions,such as those mentioned above, may be utilized by either the APCM orDPCM modems 2550 or 2560 to determine when to retransmit a long frameafter transmitting a short frame.

FIG. 25 c illustrates one embodiment of the present invention that maybe incorporated or be used in conjunction with the ITU RecommendationV.92. According to FIG. 25 c, the APCM and DPCM modems 2580 and 2590exchange CP and CPa frames 2582 and 2592, respectively. Immediatelyafter the transmission of the long CP and CPa frames 2582 and 2592, bothmodems 2580 and 2590 start transmitting short CP (CPs) and short CPa(CPas) frames 2583 and 2593, respectively. As shown, the DPCM modem 2590receives the CP frame 2582 properly. In response, the DPCM modem 2590acknowledges the CP frame 2582 with a CPas′ frame 2594. At the otherend, however, the APCM 2580 fails to receive the CPa frame 2592.Therefore, the APCM modem 2580 continues transmitting CPs frames 2583with the acknowledgement set to “0” indicating that the CPa frame 2592has not been received. As shown, the DPCM modem 2590 stops transmittingCPas′ frames 2594 and instead starts transmitting long CPa frames 2595having the acknowledgement bit set (because CP has been received), i.e.,CPa′. As shown in this embodiment, the DPCM modem 2590 may send morethan one CPa′. However, in other embodiment only a single CPa′ may besent and the DPCM modem 2590 may switch back to sending CPas′. In themean time, the APCM modem 2580 continues sending short CP frames 2583,since it has received the CPas′ frame 2594 as acknowledgement.Eventually, the APCM modem 2580 receives the long CPa frame 2595 fromthe DPCM modem 2590 and the modems move to the data phase. Theabove-mentioned triggering events or conditions may also be used here indetermining when to retransmit a long frame after transmitting a shortframe.

FIG. 26 illustrates another embodiment of the present inventionaccording to which rate negotiations between modems can be madesubstantially quicker. FIG. 26 shows a rate renegotiation exchangeprocess between an APCM modem 2610 and a DPCM modem 2620. As shown, asimilar parameter exchange process used during the modem start uptraining can be used for exchanging MP, CP and CPa. The example of FIG.26 shows a rate renegotiation process according to the ITURecommendation V.90. However, the same concept is applicable to V.34 andV.92 rate renegotiations. FIG. 26 shows a rate renegotiation initiatedby the APCM modem 2610. As shown, the modems 2610 and 2620 exchange longCP and MP frames 2612 and 2622, respectively. Afterwards, both modems2610 and 2612 start transmitting short CP (CPs) and short MP (MPs)frames 2613 and 2623, respectively. According to this example, the APCMmodem 2610 receives the MP frame 2622 first and, in response, transmitsa CPs′ frame 2614 to the DPCM modem 2620 in acknowledgement. At theother end, the DPCM modem 2620 receives the CP frame 2612 and inacknowledgement transmits an MPs′ frame 2624. At this stage, both modems2610 and 2620 quickly continue to the data phase. As a result oftransmitting short CP and MP frames, the modems 2610 and 2620 are ableto conclude the rate renegotiation much quicker.

FIG. 27 is another embodiment of the present invention for improving thefast train speed. FIG. 27 shows a fast train process between an APCMmodem 2710 and a DPCM modem 2720. During a fast train process, aparameter exchange is also used for exchanging MP, CP and CPa. Theexample of FIG. 27 shows a fast train process according to the ITURecommendation V.90. However, the same may be applied to V.34 and V.92fast trains. FIG. 27 shows a fast train process initiated by the APCMmodem 2710. As shown, the modems 2710 and 2720 exchange long CP and MPframes 2712 and 2722, respectively. Immediately thereafter, both modems2710 and 2712 start transmitting short CP (CPs) and short MP (MPs)frames 2713 and 2723, respectively. In response to receiving the MPframe 2722, the APCM modem 2710 transmits a CPs′ frame 2714 to the DPCMmodem 2720 to acknowledge the receipt. At the other end, the DPCM modem2720 receives the CP frame 2712 and in acknowledgement transmits an MPs′frame 2724. After a successful quick parameter exchange, both modems2710 and 2720 continue to the data phase. As a result of transmittingshort CP and MP frames, the fast train may be achieved in less time andmore efficiently.

FIG. 28 illustrates that the short parameter frames of the presentinvention may be combined with various other aspects of the presentinvention, such as the quick connect process. FIG. 28 shows the quickconnect process according to one aspect of the present invention. Thequick connect process, as shown, includes the use of short CP and MPframes of the present invention. FIG. 28 shows a quick connect processbetween an APCM modem 2810 and a DPCM modem 2820. During the quickconnect, MP, CP and CPa frames may be exchanged between the modems,depending upon the modem standard used for such exchange. The example ofFIG. 28 shows the quick connect according to the ITU RecommendationV.90. However, the same exchange may be applied to V.34 and V.92 quickconnect schemes. As shown, the modems 2810 and 2820 exchange long CP andMP frames 2812 and 2822, respectively. Immediately thereafter, bothmodems 2810 and 2812 start transmitting short CP (CPs) and short MP(MPs) frames 2813 and 2823, respectively. In response to receiving theMP frame 2822, the APCM modem 2810 transmits a CPs′ frame 2814 to theDPCM modem 2820 to acknowledge such receipt. At the other end, the DPCMmodem 2820 receives the CP frame 2812 and in acknowledgement transmitsan MPs′ frame 2824. After a successful quick parameter exchange, bothmodems 2710 and 2720 continue to the data phase. As a result, the quickconnect time of the present invention may be reduced even more byemploying the quick parameter exchange between the two modems.

When implemented in software, at least some elements of the presentinvention can be in the form of computer data, including, but notlimited to, any bits of information, code, etc. The data may be arrangedin group of bits or data segments and may be stored in a processorreadable medium or transmitted by a data signal embodied in a carrierwave over a transmission medium or communication link. For example, bitsof information in a CPa frame may form various data segments that can betransmitted by a data signal embodied in a carrier wave. Thecommunication link may include, but is not limited to, a telephone line,a modem connection, an Internet connection, an Integrated ServicesDigital Network (“ISDN”) connection, an Asynchronous Transfer Mode (ATM)connection, a frame relay connection, an Ethernet connection, a coaxialconnection, a fiber optic connection, satellite connections (e.g.Digital Satellite Services, etc.), wireless connections, radio frequency(RF) links, electromagnetic links, two way paging connections, etc., andcombinations thereof. The “processor readable medium” may include anymedium that can store or transfer information. Examples of the processorreadable medium include an electronic circuit, a semiconductor memorydevice, a ROM, a flash memory, an erasable ROM (EROM), a floppydiskette, a CD-ROM, an optical disk, a hard disk, a fiber optic medium,a radio frequency (RF) link, etc. The computer data signal may includeany signal that can propagate over a transmission medium such aselectronic network channels, optical fibers, air, electromagnetic, RFlinks, etc. The code segments may be downloaded via computer networkssuch as the Internet, Intranet, etc.

The present invention has been described above with reference to apreferred embodiment. However, those skilled in the art will recognizethat changes and modifications may be made to the preferred embodimentwithout departing from the scope of the present invention. These andother changes or modifications are intended to be included within thescope of the present invention, as expressed in the following claims.

1. A training method for use by a first modem to reduce a training timeassociated with exchanging training parameters with a second modem, saidtraining method comprising the steps of: transmitting a first frame tosaid second modem, said first frame including a plurality of firsttraining parameters; transmitting one or more second frames to saidsecond modem, after said step of transmitting said first frame, saidsecond frame lacking said plurality of first training parameters andbeing shorter than said first frame; receiving an acknowledgement fromsaid second modem acknowledging receipt of said first frame by saidsecond modem; continuing said step of transmitting said one or moresecond frames after said receiving said acknowledgement if said firstmodem has not transmitted an acknowledgement to said second modem toindicate receipt of a plurality of second training parameters by saidfirst modem from said second modem.
 2. The training method of claim 1,wherein said plurality of first training parameters include modulationparameters.
 3. The training method of claim 1, wherein said plurality offirst training parameters include constellation parameters.
 4. Thetraining method of claim 1 further comprising the steps of: receiving athird frame from said second modem, said third frame including saidplurality of second training parameters; and receiving one or morefourth frames from said second modem, after said step of receiving saidthird frame, said fourth frame lacking said plurality of second trainingparameters and being shorter than said third frame.
 5. The trainingmethod of claim 4, wherein said step of receiving said acknowledgementincludes receiving one of said one or more fourth frames with anacknowledgement indictor indicating receipt of said first frame by saidsecond modem.
 6. The training method of claim 4 further comprising thestep of transmitting an acknowledgement to said second modemacknowledging receipt of said third frame from said second modem.
 7. Thetraining method of claim 1, wherein each of said first frame, secondframe, third frame and fourth frame includes an acknowledgment indicatorfield.
 8. A training method for use by a first modem to reduce atraining time associated with exchanging training parameters with asecond modem, said training method comprising the steps of: receiving afirst frame from said second modem, said first frame including aplurality of first training parameters; receiving one or more secondframes from said second modem, after said step of receiving said firstframe, said second frame lacking said plurality of first trainingparameters and being shorter than said first frame; transmitting anacknowledgement to said second modem acknowledging receipt of said firstframe by said first modem; continuing said step of receiving said one ormore second frames after said transmitting said acknowledgement if saidfirst modem has not received an acknowledgement from said second modemto indicate receipt of a plurality of second training parameters by saidsecond modem from said first modem.
 9. The training method of claim 8,wherein said plurality of first training parameters include modulationparameters.
 10. The training method of claim 8, wherein said pluralityof first training parameters include constellation parameters.
 11. Thetraining method of claim 8 further comprising the steps of: transmittinga third frame to said second modem, said third frame including saidplurality of second training parameters; and transmitting one or morefourth frames to said second modem, after said step of transmitting saidthird frame, said fourth frame lacking said plurality of second trainingparameters and being shorter than said third frame.
 12. The trainingmethod of claim 11, wherein said step of transmitting saidacknowledgement includes transmitting one of said one or more fourthframes with an acknowledgement indictor indicating receipt of said firstframe from said second modem.
 13. The training method of claim 11further comprising the step of receiving an acknowledgement from saidsecond modem acknowledging receipt of said third frame from said firstmodem.
 14. The training method of claim 8, wherein each of said firstframe, second frame, third frame and fourth frame includes anacknowledgment indicator field.
 15. A first modem configured to reduce atraining time associated with exchanging training parameters with asecond modem, said first modem comprising: a transmitter configured totransmit a first frame to said second modem, said first frame includinga plurality of first training parameters, said transmitter furtherconfigured to transmit one or more second frames to said second modem,after said transmitter transmits said first frame, said second framelacking said plurality of first training parameters and being shorterthan said first frame; a receiver configured to receive anacknowledgement from said second modem acknowledging receipt of saidfirst frame by said second modem; wherein said transmitter continues totransmit one or more said second frames, after said receiver receivessaid acknowledgement, if said transmitter has not transmitted anacknowledgement to said second modem to indicate receipt of a pluralityof second training parameters by said receiver from said second modem.16. The first modem of claim 15, wherein said plurality of firsttraining parameters include modulation parameters.
 17. The first modemof claim 15, wherein said plurality of first training parameters includeconstellation parameters.
 18. The first modem of claim 15, wherein saidreceiver is further configured to receive a third frame from said secondmodem, said third frame including said plurality of second trainingparameters, and wherein said receiver is further configured to receiveone or more fourth frames from said second modem, after said receiverreceiving said third frame, said fourth frame lacking said plurality ofsecond training parameters and being shorter than said third frame. 19.The first modem of claim 18, wherein said receiver receiving saidacknowledgement includes receiving one of said one or more fourth frameswith an acknowledgement indictor indicating receipt of said first frameby said second modem.
 20. The first modem of claim 19, wherein saidtransmitter is further configured to transmit an acknowledgement to saidsecond modem acknowledging receipt of said third frame from said secondmodem.
 21. The first modem of claim 15, wherein each of said firstframe, second frame, third frame and fourth frame includes anacknowledgment indicator field.
 22. A first modem configured to reduce atraining time associated with exchanging training parameters with asecond modem, said first modem comprising: a receiver configured toreceive a first frame from said second modem, said first frame includinga plurality of first training parameters, said receiver furtherconfigured to receive one or more second frames from said second modem,after said receiver receives said first frame, said second frame lackingsaid plurality of first training parameters and being shorter than saidfirst frame; a transmitter configured to transmit an acknowledgement tosaid second modem acknowledging receipt of said first frame from saidsecond modem; wherein said receiver continues to receive one or moresaid second frames, after said transmitter transmits saidacknowledgement, if said receiver has not received an acknowledgementfrom said second modem to indicate receipt of a plurality of secondtraining parameters by said second modem from said transmitter.
 23. Thefirst modem of claim 22, wherein said plurality of first trainingparameters include modulation parameters.
 24. The first modem of claim22, wherein said plurality of first training parameters includeconstellation parameters.
 25. The first modem of claim 22, wherein saidtransmitter is further configured to transmit a third frame to saidsecond, said third frame including said plurality of second trainingparameters, and said transmitter is further configured to transmit oneor more fourth frames to said second modem, after said transmittertransmitting said third frame, said fourth frame lacking said pluralityof second training parameters and being shorter than said third frame.26. The first modem of claim 25, wherein said transmitter transmittingsaid acknowledgement includes transmitting one of said one or morefourth frames with an acknowledgement indictor indicating receipt ofsaid first frame from said second modem.
 27. The first modem of claim25, wherein said receiver is further configured to receive anacknowledgement from said second modem acknowledging receipt of saidthird frame from said first modem.
 28. The first modem of claim 22,wherein each of said first frame, second frame, third frame and fourthframe includes an acknowledgment indicator field.
 29. A computerreadable medium including a computer software product executable by aprocessor in a first modem, said computer software product for use by afirst modem to reduce a training time associated with exchangingtraining parameters with a second modem, said computer software productcomprising: code for transmitting a first frame to said second modem,said first frame including a plurality of first training parameters;code for transmitting one or more second frames to said second modem,executed after said code for transmitting said first frame, said secondframe lacking said plurality of first training parameters and beingshorter than said first frame; code for receiving an acknowledgementfrom said second modem acknowledging receipt of said first frame by saidsecond modem; continuing execution of said code for transmitting saidone or more second frames after receiving said acknowledgement if saidfirst modem has not transmitted an acknowledgement to said second modemto indicate receipt of a plurality of second training parameters by saidfirst modem from said second modem.
 30. The computer readable medium ofclaim 29, wherein said plurality of first training parameters includemodulation parameters.
 31. The computer readable medium of claim 29,wherein said plurality of first training parameters includeconstellation parameters.
 32. The computer readable medium of claim 29,wherein said computer software product further comprising: code forreceiving a third frame from said second modem, said third frameincluding said plurality of second training parameters; and code forreceiving one or more fourth frames from said second modem, executedafter said code for receiving said third frame, said fourth framelacking said plurality of second training parameters and being shorterthan said third frame.
 33. The computer readable medium of claim 32,wherein said code for receiving said acknowledgement includes code forreceiving one of said one or more fourth frames with an acknowledgementindictor indicating receipt of said first frame by said second modem.34. The computer readable medium of claim 32, wherein said computersoftware product further comprising code for transmitting anacknowledgement to said second modem acknowledging receipt of said thirdframe from said second modem.
 35. The computer readable medium of claim29, wherein each of said first frame, second frame, third frame andfourth frame includes an acknowledgment indicator field.
 36. A trainingmethod for use by a first modem to train with a second modem forreducing training time during exchange of training parameters betweensaid first modem and said second modem, said training method comprising:transmitting a long information sequence including a plurality oftraining parameters; repeatedly transmitting a number of shortinformation sequences for a predetermined period of time, after saidtransmitting said long information sequence, until receiving anacknowledgment from said second modem indicating receipt of said longinformation sequence by said second modem; and retransmitting said longinformation sequence, after said repeatedly transmitting said number ofsaid short information sequences and after expiration of saidpredetermined period of time, if said acknowledgement is not receivedfrom said second modem.
 37. The method of claim 36, wherein each of saidlong information sequence and said short information sequence includes atype portion, and wherein said type portions distinguish said longinformation sequence from said short information sequence.
 38. Themethod of claim 36, wherein said long information sequence is an MPframe and said short information sequence is an MPs frame.
 39. Themethod of claim 36 further comprising: receiving a long informationsequence including said acknowledgement from said second modem.
 40. Themethod of claim 36 further comprising: receiving a short informationsequence including said acknowledgement from said second modem.
 41. Themethod of claim 36, wherein said long information sequence is a CP frameand said short information sequence is a CPs frame.
 42. The method ofclaim 36, wherein said long information sequence is a CPa frame and saidshort information sequence is a CPas frame.
 43. The method of claim 36,wherein said method is utilized as a part of a fast train handshakebetween said first modem and said second modem.